Home
Search results “Null unique index oracle”
Oracle SQL Tutorial 21 - How to Create / Drop Indexes
 
03:58
In the last video, we wrote up the SQL to create three tables: CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, CONSTRAINT users_pk PRIMARY KEY (user_id) ); CREATE TABLE projects( project_id NUMBER, Project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL, CONSTRAINT projects_pk PRIMARY KEY (project_id), CONSTRAINT projects_users_fk FOREIGN KEY (creator) REFERENCES users (username) ON DELETE CASCADE ); CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ); I'm going to increase the size of the users table a bit by adding a first and last name column. CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, first_name VARCHAR2(50 CHAR), last_name VARCHAR2 (50 CHAR), CONSTRAINT users_pk PRIMARY KEY (user_id) ); But before we finish this design, we should consider indexing certain columns. What columns should we index? Well, as a reminder, the columns that are indexed by default are columns with the UNIQUE constraint, and those that are labeled as primary keys. Columns that are not indexed but often should be are those labeled as a foreign key. The column that jumps out the most to me is the creator column of the project table. It's the only foreign key that is not part of some index. Let's fix this by creating our first index. The way we do that is with the CREATE INDEX command. CREATE INDEX projects_creator_ix ON projects (creator) What naming convention are we following for the index? We are naming it by the table name, followed by an underscore, followed by the column, followed by an underscore, followed by an ix (for index). In this situation it does not apply, but if our foreign key column is labeled as UNIQUE, we can add the UNIQUE keyword like this: CREATE UNIQUE INDEX projects_creator_ix ON projects (creator) Now if you want to get rid of an INDEX, you can use this command: DROP INDEX projects_creator_ix Now, if we want to select data from the user table and the project table we can do that much faster. That's because the foreign key and column it references are both indexed and those are the columns we would do the join on. We will discuss how to do joins in a future video. So what are some potential problems with this database design? Overall, it is pretty good. With this design though we need to make sure there is no way for someone to update a user's username. In the next video we are going to discuss why. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 7987 Caleb Curry
Oracle - SQL - Not Null Constraint
 
05:14
Oracle - SQL - Not Null Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle - SQL - Unique Constraint
 
07:50
Oracle - SQL - Unique Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Unique and Non Unique Indexes in sql server   Part 37
 
11:02
In this video we will learn about 1. What is a Unique Index 2. Difference between unique index and unique constraint Text version of the video http://csharp-video-tutorials.blogspot.com/2012/09/unique-and-non-unique-indexes-part-37.html Slides http://csharp-video-tutorials.blogspot.com/2013/09/part-37-unique-non-unique-indexes.html All SQL Server Text Articles http://csharp-video-tutorials.blogspot.com/p/free-sql-server-video-tutorials-for.html All SQL Server Slides http://csharp-video-tutorials.blogspot.com/p/sql-server.html All Dot Net and SQL Server Tutorials in English https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd All Dot Net and SQL Server Tutorials in Arabic https://www.youtube.com/c/KudvenkatArabic/playlists
Views: 201218 kudvenkat
Oracle SQL Tutorial 20 - How to Create Composite Primary Keys
 
07:02
This video is going to be a tutorial on how to create composite and compound keys. The difference between a composite and compound key is that a composite key can consist of any columns while a compound key has to consist of columns that are all keys themselves. We will be working with a compound key because we are going to be using the an intermediary table that has two foreign keys. The combination of both of the keys have to be unique. First, if we have any other CREATE TABLE commands, we are going to comment those out. We will space out the CREATE TABLE to have each column on a line, then we will add constraints as needed. CREATE TABLE project_users( project_id, user_id ) Now, let's add the data types: CREATE TABLE project_users( project_id NUMBER, user_id NUMBER } Now, what about some column attributes? I'm going to make both of the columns NOT NULL because we always want the rows to have a user and a project: CREATE TABLE project_users( project_id NUMBER NOT NULL, user_id NUMBER NOT NULL } Now, let's add the foreign key constraints. Now, what do we name these? We are going to add a primary key that covers both of these columns, so I'm going to be a sinner and not give these constraints names: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id), user_id NUMBER NOT NULL REFFERENCES users (user_id) ) Now, the way we have it now is that if we delete a project in the project table, and there are any rows in the project_users table, it will throw an error and prevent deletion. I would prefer for it to also delete any project members. That would make sense because if you delete a project we want it to delete the associate between that project and certain users. The same goes for if we delete a user, we want their association with a certain project to be deleted. To do this, we need to add the ON DELETE command: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, ) Finally, let's learn how to create a compound or composite key. literally, the only difference is that you put a comma and add the second table inside of the parenthesis. CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ) Now, the combination of project_id and user_id cannot be null, is always unique, and has an index. The only thing we should do now is add a few indexes. We aren't done yet...In the next video we are going to figure out what columns would benefit from indexes and we'll add them to it. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 9966 Caleb Curry
Differences between primary key and unique key - SQL Server Interview Questions
 
06:07
Hi Friends, In this in this session we are going to learn the differences between primary key and unique key This is one of the most frequently asked sql server interview questions. Before we discuss the difference between primary key and unique key, let's see what a primary key is and what a unique key is. Primary Key: Primary key is a key which uniquely identifies each row/record in the table. This implies if you have a primary key on a table, you can identify each and every row in that table uniquely using primary key. Unique Key: Unique key constraint enforces the uniqueness on the columns in which it is defined. That is Unique key will make sure only unique values are allowed in the columns in which it is defined. Similarities: Both Primary key and unique Key enforces uniqueness on the columns on which they are defined. • Primary key and unique Key columns allow only unique values. • Primary key and unique Key columns will avoid duplicates • Both Primary key and unique Key columns uniquely identifies each row/record in the table Differences: PRIMARY KEY UNIQUE KEY Primary Key Does not allow duplicates Unique key allows only one NULL A table can have only 1 Primary Key A table can have multiple Unique Keys By default Primary Key creates a Unique Clustered Index on the table By default Unique Key creates a Unique Non-Clustered Index on the table. I hope this session is clear and i hope this knowldge should help you in interviews. Please share your valuable comments & sugesstions. Also, subscriber to my channel for more sql server interview questions and answers. Bye bye & Have a good day.
Views: 37993 TheSSScreations
SQL tutorial 62: Indexes In Oracle Database By Manish Sharma RebellionRider
 
04:03
Watch and learn concepts of SQL Index In Oracle Database. In this tutorial you will learn about B-Tree Index and Function based Index. ------------------------------------------------------------------------ ►►►LINKS◄◄◄ Blog : Previous Tutorial ► ------------------------------------------------------------------------- ►►►Help Me In Getting A Job◄◄◄ ►Help Me In Getting A Good Job By Connecting With Me on My LinkedIn and Endorsing My Skills. All My Contact Info is Down Below. You Can Also Refer Me To Your Company Thanks ------------------------------------------------------------------------- Copy Cloud referral link || Use this link to join copy cloud and get 20GB of free storage https://copy.com?r=kb4rc1 -------------------------------------------------------------------------- ►Make sure you SUBSCRIBE and be the 1st one to see my videos! -------------------------------------------------------------------------- Amazon Wishlist: http://bit.ly/wishlist-amazon ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ►►►Find me on Social Media◄◄◄ Follow What I am up to as it happens on https://twitter.com/rebellionrider https://www.facebook.com/imthebhardwaj http://instagram.com/rebellionrider https://plus.google.com/+Rebellionrider http://in.linkedin.com/in/mannbhardwaj/ http://rebellionrider.tumblr.com/ http://www.pinterest.com/rebellionrider/ You can also Email me at for E-mail address please check About section Please please LIKE and SHARE my videos it makes me happy. Thanks for liking, commenting, sharing and watching more of our videos This is Manish from RebellionRider.com ♥ I LOVE ALL MY VIEWERS AND SUBSCRIBERS
Views: 40099 Manish Sharma
Oracle - SQL - Check Constraint
 
04:15
Oracle - SQL - Check Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle - SQL - Primary Key Constraint
 
04:10
Oracle - SQL - Primary Key Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
DIFFERENCE BETWEEN PRIMARY KEY AND UNIQUE KEY CONSTRAINT IN ORACLE SQL
 
06:47
This video tutorial explains about the difference between primary key and unique key in oracle sql which is also a to be asked interview quiestion. After watching this video you will be able to explain the difference between both the constraints.
Views: 1868 Kishan Mashru
Table Constraints in SQL: NOT NULL, DEFAULT, UNIQUE, and CHECK
 
03:44
This SQL tutorial discusses the common constraints one can place on a table: NOT NULL, DEFAULT, UNIQUE, and CHECK, including the purpose of each constraint, as well as how to apply each constraint to a table during table creation. 0:24 NOT NULL Constraint 0:56 DEFAULT Constraint 2:03 UNIQUE Constraint 2:34 CHECK Constraint
Views: 8561 1Keydata
SQL Constraints - NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default
 
10:17
SQL is a standard Structured query language for storing, manipulating and retrieving data in databases. NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default 1) NOT NULL - Ensures that a column cannot have a NULL value 2) UNIQUE - Ensures that all values in a column are different 3) PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table 4) FOREIGN KEY - Uniquely identifies a row/record in another table. The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table. prevents invalid data and destroy links between tables. 5) CHECK - Ensures that all values in a column satisfies a specific condition 6) DEFAULT - Sets a default value for a column when no value is specified 7) INDEX - Used to create and retrieve data from the database very quickly.
Views: 12 R K
Constraint In Oracle PL SQL
 
06:47
Constraint In Oracle PL SQL oracle tutorial for beginners A) UNIQUE CONSTRAINT : A unique constraint is uniquely defines a record. Its value is not repeated. It can be null. B)NOT NULL CONSTRAINT: Not null constraint restrict from inserting null values. If we want some columns does not take null values then we can use this constraint. C)CHECK CONSTRAINT: A check constraint allows you to specify a condition on particular column in a table. we can add our custom logical conditions. CREATE TABLE TEST2 ( ID VARCHAR2(10) UNIQUE, NAME VARCHAR2(50), DEPT VARCHAR2(10) NOT NULL, AGE NUMBER(10), CHECK (AGE BETWEEN 18 and 60) ); #techquerypond https://techquerypond.wordpress.com https://techquerypond.com https://twitter.com/techquerypond
Views: 174 Tech Query Pond
UNIQUE KEY CONSTRAINT IN ORACLE SQL WITH EXAMPLE
 
14:37
This is a free video tutorial by Kishan mashru on unique constraint in Oracle SQL, the video firstly explains what unique constraint is and how it can be used along with its various limitations, then the video gives perfect examples to understand how to create a unique key at the column level or inline, or at the table level i.e out of line. The video gives a demonstration on ALTER TABLE ADD CONSTRAINT and ALTER TABLE DROP CONSTRAINT statements also.
Views: 949 Kishan Mashru
4- Oracle DB - Primary Foreign Unique Not Null Check Composite Keys Table Level and Column Level.avi
 
37:25
Oracle DB - Primary Foreign Unique Not Null Check Composite Keys Table Level and Column Level
Views: 2659 Adel Sabour
Oracle - SQL - Foreign Key Constraint
 
06:15
Oracle - SQL - Foreign Key Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
45. Primary Key and Foreign Key Constraints in PL/SQL Oracle
 
12:36
In this video you will learn about Primary Key and Foreign Key Constraints in PL/SQL Oracle. For Support =========== Email: [email protected] Contact Form: http://www.learninhindi.com/home/contact Our Social Media ================ Facebook: https://www.facebook.com/LearnInHindi Twitter: https://twitter.com/LearnInHindi For Training & Videos ===================== For more videos and articles visit: http://www.learninhindi.com Free Java Programming In Hindi Course ===================================== https://www.youtube.com/playlist?list=PLOZ3jentlCDAwwhMyoLISrxkXTADGp7PH Free Oracle PL/SQL Programming In Hindi Course ============================================== https://www.youtube.com/playlist?list=PLB5DA82419C2D99B6 Free C Programming In Hindi Course ================================== https://www.youtube.com/playlist?list=PLOZ3jentlCDAxKpBLMWogxSdy6BZcsAJq Trips & Tricks Channel ====================== https://www.youtube.com/channel/UCGmLfkuCo-3lHHJXRJ9HUMw Programming in Hindi Channel ============================ https://www.youtube.com/channel/UCudElIDgwNrybeAvXIy1HZQ
Views: 9633 ITORIAN
Constraints Part-2 NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default
 
13:22
SQL is a standard Structured query language for storing, manipulating and retrieving data in databases. NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default 1) NOT NULL - Ensures that a column cannot have a NULL value 2) UNIQUE - Ensures that all values in a column are different 3) PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table 4) FOREIGN KEY - Uniquely identifies a row/record in another table. The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table. prevents invalid data and destroy links between tables. 5) CHECK - Ensures that all values in a column satisfies a specific condition 6) DEFAULT - Sets a default value for a column when no value is specified 7) INDEX - Used to create and retrieve data from the database very quickly.
Views: 7 R K
Oracle Constraints Easy way
 
59:07
Oracle Constraints Easy way
Views: 80 laks nayan
Foreign Key | Database Management System
 
06:29
To ask your doubts on this topic and much more, click on this Direct Link: http://www.techtud.com/video-lecture/lecture-foreign-key IMPORTANT LINKS: 1) Official Website: http://www.techtud.com/ 2) Virtual GATE: http://virtualgate.in/login/index.php Both of the above mentioned platforms are COMPLETELY FREE, so feel free to Explore, Learn, Practice & Share! Our Social Media Links: Facebook Page: https://www.facebook.com/techtuduniversity Facebook Group: https://www.facebook.com/groups/virtualgate Google+ Page: https://plus.google.com/+techtud/posts Last but not the least, SUBSCRIBE our YouTube channel to stay updated about the regularly uploaded new videos.
Views: 251126 Techtud
47. UNIQUE KEY in SQL (Hindi)
 
16:42
Please Subscribe Channel Like, Share and Comment Visit : www.geekyshows.com
Views: 17313 Geeky Shows
Oracle - SQL - Constraints
 
07:11
Oracle - SQL - Constraints Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle SQL Tutorial For Beginners | Oracle SQL Online Training - Session 1
 
52:39
Course : Oracle SQL Online Training Mode of Training : Online Duration : 40 Hours Timings : Flexible Oracle SQL Online Training Demo Registration Link : http://svsoftsolutions.com/demo.aspx Introduction to SQL What is SQL? What Can SQL do? RDBMS SQL Syntax Database Tables SQL Statements Overview of Most Important SQL Commands SELECT UPDATE DELETE INSERT CREATE TABLE ALTER TABLE DROP TABLE CREATE INDEX DROP INDEX SQL SELECT Statement SELECT syntax Demo Database SELECT Column Example SELECT * Example SQL Distinct SELECT DISTINCT Statement SELECT DISTINCT Syntax SELECT DISTINCT Example SQL WHERE Clause WHERE Clause WHERE Clause Example Operators in the WHERE Clause SQL AND & OR Operators AND Operator Example OR Operator Example Combining AND & OR SQL ORDER BY ORDER BY Syntax ORDER BY Example ORDER BY DESC Example ORDER BY Several Column Examples SQL Insert Into INSERT INTO Syntax INSERT INTO Examples Insert Data into Specified Columns SQL UPDATE UPDATE Syntax UPDATE Example Watch out UPDATE statement. SQL DELETE DELETE Syntax DELETE Examples Delete All the Data SQL Aliases SQL Alias Syntax for Columns Alias Example for Table Columns Alias Example for Tables. SQL Joins Different SQL JOINs INNER JOIN LEFT OUTER JOIN RIGHT OUTER JOIN FULL OUTER JOIN SQL UNION UNION Syntax UNION Example UNION ALL Syntax UNION ALL Example SQL Insert Into Select INSERT INTO SELECT Syntax INSERT INTO SELECT Examples SQL Create Table CREATE TABLE Syntax CREATE TABLE Example SQL Constraints CREATE TABLE + CONSTRAINT Syntax NOT NULL Constraint UNIQUE Constraint UNIQUE Constraint on CREATE TABLE UNIQUE Constraint on ALTER TABLE To DROP a UNIQUE Constraint PRIMARY KEY Constraint PRIMARY KEY Constraint on CREATE TABLE PRIMARY KEY Constraint on ALTER TABLE To DROP a PRIMARY KEY Constraint FOREIGN KEY Constraint FOREIGN KEY Constraint on CREATE TABLE FOREIGN KEY Constraint on ALTER TABLE To DROP a FOREIGN KEY Constraint CHECK Constraint CHECK Constraint on CREATE TABLE CHECK Constraint on ALTER TABLE To DROP a CHECK Constraint DEFAULT Constraint on CREATE TABLE DEFAULT Constraint on ALTER TABLE To DROP a DEFAULT Constraint SQL Create Index CREATE INDEX Syntax CREATE UNIQUE INDEX Syntax CREATE INDEX Example SQL DROP Command The DROP INDEX Statement The DROP TABLE Statement The DROP DATABASE Statement The TRUNCATE TABLE Statement SQL ALTER Command The ALTER TABLE Statement ALTER TABLE Example Change Data Type Example DROP COLUMN Example SQL VIEWS CREATE VIEW Statement CREATE VIEW Syntax CREATE VIEW Examples CREATE OR REPLACE VIEW Syntax Dropping a View SQL NULL Values Working with NULL Values IS NULL IS NOT NULL SQL NULL Functions NVL COALESCE For more details visit our website : www.svsoftsolutions.com Or reach us @ USA : +1-845-915-8712 (Toll Free), India : +91-9642373173
Views: 1063 SV Soft Solutions
Oracle - SQL - Managing Constraints
 
06:01
Oracle - SQL - Managing Constraints Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
mysql tutorial for beginners (6/8) : Indexes
 
05:48
mysql tutorial for beginners (6/8) : Indexes As things stand, the table students works and can be searched without problem by MySQL—until it grows to more than a couple of hundred rows, At that point, database accesses will get slower and slower with every new row added, because MySQL has to search through every row whenever a query is issued. This is like searching through every book in a library whenever you need to look something up. Of course, you don’t have to search libraries that way, because they have either a card index system or, most likely, a database of their own. The way to achieve fast searches is to add an index, either when creating a table or at any time afterward. But the decision is not so simple. For example, there are different index types such as a regular INDEX, PRIMARY KEY, and FULLTEXT. Also, you must decide which columns require an index, a judgment that requires you to predict whether you will be searching any of the data in that column. And even when you’ve decided that, you still have the option of reducing index size by limiting the amount of each column to be indexed. If we imagine the searches that may be made on the students table, it becomes apparent that all of the columns may need to be searched. Anyway, go ahead and add an index to each of the columns, using the commands: ALTER TABLE students ADD INDEX(name(3)); An alternative to using ALTER TABLE to add an index is to use the CREATE INDEX command. They are equivalent, except that CREATE INDEX cannot be used for creating a PRIMARY KEY CREATE INDEX surname ON students (surname(5)); DESCRIBE students; These commands create indexes on both the name and surname columns, limiting name index to only the first 3 characters, and surname index to the first 5 characters. For instance, when MySQL indexes the following name: SAFAA It will actually store in the index only the first 3 characters: SAF This is done to minimize the size of the index, and to optimize database access speed. DESCRIBE command shows the key MUL for each column. This key means that multiple occurrences of a value may occur within that column, which is exactly what we want, as name or surname may appear many times. You don’t have to wait, until after creating a table to add indexes. In fact, doing so can be time-consuming, as adding an index to a large table can take a very long time. Therefore, let’s look at a command that creates the table students with indexes already in place. CREATE TABLE students ( Id_studnet SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, name VARCHAR(10) NOT NULL, surname VARCHAR(20) NOT NULL, email VARCHAR(30) NOT NULL, INDEX(name(3)), INDEX(surname(5)), ,PRIMARY KEY(id_studnet),UNIQUE(email)); Another important index, PK, its single unique key for each student to enable instant accessing of a row. The importance of having a key with a unique value for each row will come up when we start to combine data from different tables. You can add PK, while you create the table at the first time, or later by issuing the following command: ALTER TABLE students ADD PRIMARY KEY(id_student); The last important index, FULLTEXT index Unlike a regular index, MySQL’s FULLTEXT allows super-fast searches of entire columns of text. It stores every word in every data string in a special index that you can search using “natural language,” in a similar manner to using a search engine. It’s not strictly true that MySQL stores all the words in a FULLTEXT index, because it has a built-in list of more than 500 words that it chooses to ignore because they are so common that they aren’t very helpful for searching anyway. This list, called stopwords, includes the, as, is, of, and so on. The list helps MySQL run much more quickly when performing a FULLTEXT search and keeps database sizes down. FULLTEXT indexes can be created for CHAR, VARCHAR, and TEXT columns only. A FULLTEXT index definition can be given in the CREATE TABLE statement when a table is created, or added later using ALTER TABLE (or CREATE INDEX). Adding a FULLTEXT index to the table students for the columns name and surname ALTER TABLE classics ADD FULLTEXT(name,surname); this index is in addition to the ones already created and does not affect them You can now perform FULLTEXT searches across this pair of columns. If you find that MySQL is running slower than you think it should be when accessing your database, the problem is usually related to your indexes. Either you don’t have an index where you need one, or the indexes are not optimally designed. Tweaking a table’s indexes will often solve such a problem. In the next tutorial, we will learn about, using FOREIGN KEY Constraints and how to join tables together. Subscribe for more: ---------------------------------------------------------------------------- https://www.youtube.com/subscription_center?add_user=saf3al2a SWE.Safaa Al-Hayali - saf3al2a
Views: 26073 Safaa Al-Hayali
Oracle SQL Tutorial For Beginners | Oracle SQL Online Training - Session 2
 
01:03:12
Course : Oracle SQL Online Training Mode of Training : Online Duration : 40 Hours Timings : Flexible Oracle SQL Online Training Demo Registration Link : http://svsoftsolutions.com/demo.aspx Introduction to SQL What is SQL? What Can SQL do? RDBMS SQL Syntax Database Tables SQL Statements Overview of Most Important SQL Commands SELECT UPDATE DELETE INSERT CREATE TABLE ALTER TABLE DROP TABLE CREATE INDEX DROP INDEX SQL SELECT Statement SELECT syntax Demo Database SELECT Column Example SELECT * Example SQL Distinct SELECT DISTINCT Statement SELECT DISTINCT Syntax SELECT DISTINCT Example SQL WHERE Clause WHERE Clause WHERE Clause Example Operators in the WHERE Clause SQL AND & OR Operators AND Operator Example OR Operator Example Combining AND & OR SQL ORDER BY ORDER BY Syntax ORDER BY Example ORDER BY DESC Example ORDER BY Several Column Examples SQL Insert Into INSERT INTO Syntax INSERT INTO Examples Insert Data into Specified Columns SQL UPDATE UPDATE Syntax UPDATE Example Watch out UPDATE statement. SQL DELETE DELETE Syntax DELETE Examples Delete All the Data SQL Aliases SQL Alias Syntax for Columns Alias Example for Table Columns Alias Example for Tables. SQL Joins Different SQL JOINs INNER JOIN LEFT OUTER JOIN RIGHT OUTER JOIN FULL OUTER JOIN SQL UNION UNION Syntax UNION Example UNION ALL Syntax UNION ALL Example SQL Insert Into Select INSERT INTO SELECT Syntax INSERT INTO SELECT Examples SQL Create Table CREATE TABLE Syntax CREATE TABLE Example SQL Constraints CREATE TABLE + CONSTRAINT Syntax NOT NULL Constraint UNIQUE Constraint UNIQUE Constraint on CREATE TABLE UNIQUE Constraint on ALTER TABLE To DROP a UNIQUE Constraint PRIMARY KEY Constraint PRIMARY KEY Constraint on CREATE TABLE PRIMARY KEY Constraint on ALTER TABLE To DROP a PRIMARY KEY Constraint FOREIGN KEY Constraint FOREIGN KEY Constraint on CREATE TABLE FOREIGN KEY Constraint on ALTER TABLE To DROP a FOREIGN KEY Constraint CHECK Constraint CHECK Constraint on CREATE TABLE CHECK Constraint on ALTER TABLE To DROP a CHECK Constraint DEFAULT Constraint on CREATE TABLE DEFAULT Constraint on ALTER TABLE To DROP a DEFAULT Constraint SQL Create Index CREATE INDEX Syntax CREATE UNIQUE INDEX Syntax CREATE INDEX Example SQL DROP Command The DROP INDEX Statement The DROP TABLE Statement The DROP DATABASE Statement The TRUNCATE TABLE Statement SQL ALTER Command The ALTER TABLE Statement ALTER TABLE Example Change Data Type Example DROP COLUMN Example SQL VIEWS CREATE VIEW Statement CREATE VIEW Syntax CREATE VIEW Examples CREATE OR REPLACE VIEW Syntax Dropping a View SQL NULL Values Working with NULL Values IS NULL IS NOT NULL SQL NULL Functions NVL COALESCE For more details visit our website : www.svsoftsolutions.com Or reach us @ USA : +1-845-915-8712 (Toll Free), India : +91-9642373173
Views: 54 SV Soft Solutions
SQL Server 28 - Composite Primary Key
 
04:55
The previous video had these tables: CREATE TABLE Species( ID INT PRIMARY KEY IDENTITY, Species VARCHAR(50) NOT NULL UNIQUE, FriendlyName VARCHAR(50) NOT NULL ); CREATE TABLE Animals( ID INT PRIMARY KEY IDENTITY, Name VARCHAR(50) NOT NULL, Species INT NOT NULL REFERENCES Species(ID), ContactEmail VARCHAR(50) NOT NULL UNIQUE ); These column attributes are all examples of constraints. To be more specific, they are known as column-level constraints. Sometimes you need to create what is known as a table-level constraint. To illustrate this, we are going to create a new table that shows this in action. Remember that we are trying to create an animal dating site. A specific animal can create an account on our website and say what kind of species he or she is interested in. One specific animal can be interested in multiple species and an individual species can be liked by many animals. Therefore, it is a many to many relationship. We already have a Species table and an Animals table, so we need an intermediary table to associate animals with species: CREATE TABLE Interests( AnimalID INT NOT NULL REFERENCES Animals(ID), SpeciesID INT NOT NULL REFERENCES Species(ID) ); But now, we want to create a composite primary key, the combination of both columns. A column-level attribute is not capable of doing this because it is associated with just one column. Let's create a table-level constraint. To do this we add the constraint as if it's another column: CREATE TABLE Interests( AnimalID INT NOT NULL REFERENCES Animals(ID), SpeciesID INT NOT NULL REFERENCES Species(ID), PRIMARY KEY (AnimalID, SpeciesID) ); The downside here is that we cannot create a foreign key to reference this composite key. If for some reason we have to be able to reference an individual interest in another table, we would create an ID column and put a UNIQUE constraint on the combination of AnimalID and SpeciesID. Then we could reference an individual ID. Now, in SSMS, inside of our tables key folder you can find the composite key. Unfortunately, SSMS defaults to a pretty ugly name for our primary key constraint. Fortunately, we can actually give names to our constraints. That's what we will be doing in the next video. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 8002 Caleb Curry
Oracle Database Indexes: Myths, Tips and Tricks
 
09:04
In this tutorial, OCM John Watson will - via demonstrations - debunk these myths: Myth #1: Oracle Database does not index NULL Myth #2: A search that includes wildcards can't use an index if the wildcard precedes the string. Myth #3: Oracle will not use a function-based index unless the FBI is coded in the predicate. Myth #4: Indexes always help. The more indexes the better. See http://skillbuilders.com/free-oracle-tutorials for gigabytes of free Oracle video tutorials.
Views: 16120 SkillBuilders
SQL tutorials 17: SQL Primary Key constraint,  Drop primary Key
 
09:22
Blog link: http://www.rebellionrider.com/sql-primary-key.htm SQL tutorial on Primary key / SQL Primary key, In this tutorial you will learn about simple primary key, composute primary key, how to drop primary key. defining primary key using create table and alter table along with many other things. Tool used in this tutorial is SQL Developer. This tutorial series is part of SQL expert exam certification training. if you are preparing for SQL certification you can use my tutorials. This SQL Tutorial is a part of free training. Copy Cloud referral link || Use this link to join copy cloud and get 20GB of free storage https://copy.com?r=j7eYO7 Contacts E-Mail [email protected] Twitter https://twitter.com/rebellionrider Instagram http://instagram.com/rebellionrider Facebook. https://www.facebook.com/imthebhardwaj Linkedin. http://in.linkedin.com/in/mannbhardwaj/ Thanks for linking, commenting, sharing and watching more of our videos This is Manish from RebellionRider.com So Primary Key There are two types of Primary keys First is Simple primary Key: Primary key which Involves only one column and Second is Composite Primary Key: Primary Key which involves more than one column. We will start with Simple primary key. You can create Primary key either with Create Table statement of by using Alter table Statement. Let's define simple primary key using create table statements. With create table statement we can either define primary key at column level or at table level. We will start with defining Primary key at column level using create table statement. You just have to put keyword Primary key after data type and size of column while defining a column of a table. Here oracle server will create a primary key on product id with default constraint name which will be slightly difficult to understand. You can give your own name to your constraint which is also a good practice.
Views: 98007 Manish Sharma
What is the Difference between Primary Key and Unique Key - Database Tutorial 14
 
04:51
Database Tutorial. This video is about Database Fundamentals. I hope this series of videos can help those who want to be Database Professionals. I will cover various database technologies including Oracle Database, Microsoft SQL Server database and Sybase. Video: What is the Difference between Primary Key and Unique Key (Video 14 in the Database Tutorial Series) (Common for Oracle/Microsft SQL Server/Sybase /MySQL)
Views: 33717 Sam Dhanasekaran
Oracle SQL Tuning with NOT NULL Constraints
 
02:28
Learn how to tune SQL with Constraints! In this lesson (3 of 5), OCM John Watson from SkillBuilders demonstrates how to improve query performance by adding not null constraints. See all lessons, free at http://www.skillbuilders.com/oracle-database-sql-tuning-with-constraints.
Views: 390 SkillBuilders
Oracle SQL Tutorial 6 - Relationships and Primary and Foreign Keys - Database Design Primer 3
 
29:40
HAPPY VALENTINES DAY!!! Let's talk relationships.. This is the 6th video in your Oracle Database series. We are discussing database relationships which are a key feature of relational database management systems. We first discussed entities and attributes. I talked about how each entity is assigned a table and each attribute is a column within a table. We moved on to the three kinds of relationships. The first was one-to-one. This describes an entity and an attribute. A piece of data that is exclusive to an entity is, by definition, an attribute of that entity. This is stored in one table with the attribute being a column within this table. The second relationship is one-to-many. This relationship is between two entities. The way we properly store this in a database is using a foreign key in the child table. Remember, the child table is the entity on the many side of the one-to-many relationship. Every row within the child table will have a value for the foreign key that references a primary key in the parent table. This assumes that the foreign key field is not optional (NOT NULL). If the foreign key is optional, than a reference is not required but any reference must be valid. The third kind of relationship is a many-to-many relationship. In this situation, we need 3 tables. The many-to-many relationship is broken up into two one-to-many relationships. The intermediary table will associate each entity from one table with the appropriate entities in the other table. There is debate as to whether this table needs a primary key. This is because you can intact use the combination of two foreign keys as a primary key. This works because we will never have two duplicate rows within the intermediary table and the two foreign keys work as a compound key because of this. We finally discussed primary keys and foreign keys. Primary keys are used to keep each row inside of a table unique. If this key is a computer generated number it is known as a surrogate key, otherwise it is known as a natural key. Natural keys have real world meaning. For example, a social security number may work, or an email address (in some situations), etc. Whichever type of key you choose is solely up to you and/or the company you may be working for. HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://Twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 42104 Caleb Curry
13.49 PRIMARY KEY, UNIQUE, FOREIGN KEY, REFERENCES, CONSTRAINT
 
06:33
Komplette Liste der Videos und zusätzliches Material auf http://datenbankenlernen.de Informatik, Uni Saarland: Bachelor: http://www.cs.uni-saarland.de/index.php?id=52&L=1&source=1349 Master: http://www.cs.uni-saarland.de/index.php?id=132&L=1&source=1349 Ph.D./Grad School: http://gradschool.cs.uni-saarland.de/&source=1349
Tutorial 43 : INDEX in Oracle || BITMAP INDEX.
 
08:32
Hi Friends! Here we are learning about BITMAP Index. Help the concept is clear to you. Please give me your feedback in Comment Box. Thanks. Happy Coding.
Views: 114 YourSmartCode
Advantages and disadvantages of indexes in sql server   Part 38
 
12:20
In this video we will learn about 1. Advantages and disadvantages of indexes 2. The types of queries that can benefit from indexes 3. Covering Queries Text version of the video http://csharp-video-tutorials.blogspot.com/2012/09/advantages-and-disadvantages-of-indexes.html Slides http://csharp-video-tutorials.blogspot.com/2013/09/part-38-adv-dis-adv-of-indexes.html All SQL Server Text Articles http://csharp-video-tutorials.blogspot.com/p/free-sql-server-video-tutorials-for.html All SQL Server Slides http://csharp-video-tutorials.blogspot.com/p/sql-server.html All Dot Net and SQL Server Tutorials in English https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd All Dot Net and SQL Server Tutorials in Arabic https://www.youtube.com/c/KudvenkatArabic/playlists
Views: 155608 kudvenkat
Unique Key Concept
 
02:53
http://zerotoprotraining.com Unique Key Concept Category: Oracle SQL Tags: Unique Key
Views: 2701 HandsonERP
How to create Unique Constraint on Column for already existing Table - Part 97
 
04:59
SQL Server / T-SQL Tutorial Scenario: You are working as SQL Server developer, you need to create Unique Constraint on already existing table called dbo.Customer on column SSN. Link to scripts used in SQL Server / TSQL Tutorial Video http://www.techbrothersit.com/2016/05/how-to-create-unique-constraint-on_6.html Check out our website for Different SQL Server, MSBI tutorials and interview questions such as SQL Server Reporting Services(SSRS) Tutorial SQL Server Integration Services(SSIS) Tutorial SQL Server DBA Tutorial SQL Server / TSQL Tutorial ( Beginner to Advance) http://www.techbrothersit.com/
Views: 887 TechBrothersIT
SQL Constraints
 
10:54
Learn more on www.pravendragaur.com Constraints are the rules which applied on data columns on table. These are used to limit the type of data that can go into a table. This ensures the accuracy and reliability of the data in the database. Constraints could be column level or table level. Column level constraints are applied only to one column, whereas table level constraints are applied to the whole table. Types of Constraints 1. Unique 2. Not null 3. Primary Key 4. Check 5. Foreign Key
Views: 144 Pravendra Gaur
Learn Oracle | SQL Operators and their Precedence
 
05:06
Pebbles present, Learn Oracle 10g with Step By Step Video Tutorials. Learn Oracle 10g Tutorial series contains the following videos : Learn Oracle - History of Oracle Learn Oracle - What is Oracle - Why do we need Oracle Learn Oracle - What is a Database Learn Oracle - What is Grid Computing Learn Oracle - What is Normalization Learn Oracle - What is ORDBMS Learn Oracle - What is RDBMS Learn Oracle - Alias Names, Concatenation, Distinct Keyword Learn Oracle - Controlling and Managing User Access (Data Control Language) Learn Oracle - Introduction to SQL Learn Oracle - Oracle 10g New Data Types Learn Oracle - How to Alter a Table using SQL Learn Oracle - How to Create a Package in PL SQL Learn Oracle - How to Create a Report in SQL Plus Learn Oracle - How to Create a Table using SQL - Not Null, Unique Key, Primary Key Learn Oracle - How to Create a Table using SQL Learn Oracle - How to Create a Trigger in PL SQL Learn Oracle - How to Delete Data from a Table using SQL Learn Oracle - How to Drop and Truncate a Table using SQL Learn Oracle - How to Insert Data in a Table using SQL Learn Oracle - How to open ISQL Plus for the first time Learn Oracle - How to Open SQL Plus for the First Time Learn Oracle - How to Update a Table using SQL Learn Oracle - How to use Aggregate Functions in SQL Learn Oracle - How to use Functions in PL SQL Learn Oracle - How to use Group By, Having Clause in SQL Learn Oracle - How to Use Joins, Cross Join, Cartesian Product in SQL Learn Oracle - How to use Outer Joins (Left, Right, Full) in SQL Learn Oracle - How to use the Character Functions, Date Functions in SQL Learn Oracle - How to use the Merge Statement in SQL Learn Oracle - How to use the ORDER BY Clause with the Select Statement Learn Oracle - How to use the SELECT Statement Learn Oracle - How to use the Transactional Control Statements in SQL Learn Oracle - How to use PL SQL Learn Oracle - Data Types in PL SQL Learn Oracle - Exception Handling in PL SQL Learn Oracle - PL SQL Conditional Logics Learn Oracle - PL SQL Cursor Types - Explicit Cursor, Implicit Cursor Learn Oracle - PL SQL Loops Learn Oracle - Procedure Creation in PL SQL Learn Oracle - Select Statement with WHERE Cause Learn Oracle - SQL Operators and their Precedence Learn Oracle - Using Case Function, Decode Function in SQL Learn Oracle - Using Logical Operators in the WHERE Clause of the Select Statement Learn Oracle - Using Rollup Function, Cube Function Learn Oracle - Using Set Operators in SQL Learn Oracle - What are the Different SQL Data Types Learn Oracle - What are the different types of Databases Visit Pebbles Official Website - http://www.pebbles.in Subscribe to our Channel – https://www.youtube.com/channel/UCNNjWVsQqaMYccY044vtHJw?sub_confirmation=1 Engage with us on Facebook at https://www.facebook.com/PebblesChennai Please Like, Share, Comment & Subscribe
Views: 634 Pebbles Tutorials
ADD CONSTRAINTS to a new table
 
21:45
This video explains what are primary key,not null,unique,default,check constraints and how to add constraints to the columns in a table while the creation of a new table. link to HOW to add constraint while creating table: https:// https://www.youtube.com/watch?v=dh_UKs-LnK8 link to how to add new columns with constraints : https://www.youtube.com/watch?v=UNAatxnnwB8 link to how to add constraints to existing column https://www.youtube.com/watch?v=02_fXRQpwSc how to drop all constraints on the table: https://www.youtube.com/watch?v=CM7FPqIr6gc subscribe - https://www.youtube.com/channel/UCNl7...
Views: 570 kwl zerotwonine
How to create Unique Constraint on Multiple Columns in SQL Server - SQL Server/TSQL Tutorial Part 96
 
07:57
SQL Server / TSQL Tutorial Scenario: If you have noticed the insert statement, In First Record I have put both Null values for FirstName and Last Name. In 2nd record I used the value 'Aamir' for first name and Null for Last Name. In 3rd record vice versa of 2nd record. From here what we understand that the unique constraint is working on both column values. As long as the combined value from both columns is unique, it is going to let us insert even one of them is null. Link to scripts used in SQL Server / TSQL Tutorial Video http://www.techbrothersit.com/2016/05/how-to-create-unique-constraint-on.html Check out our website for Different SQL Server, MSBI tutorials and interview questions such as SQL Server Reporting Services(SSRS) Tutorial SQL Server Integration Services(SSIS) Tutorial SQL Server DBA Tutorial SQL Server / TSQL Tutorial ( Beginner to Advance) http://www.techbrothersit.com/
Views: 2169 TechBrothersIT
Unique Key Constraint in MySQL
 
05:46
The UNIQUE constraint uniquely identifies each record in a database table. The UNIQUE and PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint defined on it. Note that you can have many UNIQUE constraints per table, but only one PRIMARY KEY constraint per table. If you like our video please subscribe our channel. And visit our website http://successsole.com/ LIke us on Facebook- https://www.facebook.com/successsole/ Follow us on twitter- https://twitter.com/Successsole_twr THANK YOU!!
Views: 1709 Success Sole
Oracle SQL Tutorial 14 - Column-Level and Table-Level Constraints
 
04:15
In the previous video we talked about adding constraints at the column-level. We made it nice and simple by only requiring a few keywords, but the problem we were having is that we could not assign a name to the constraint, which many people like to do so we can reference easily if we need to at a later time. To do this, it requires a little bit more typing, but it will give us extra flexibility and many consider it to be the higher quality approach to adding constraints. Let's go though a simple example. Let's say we have a users table with a user_id column that we want to make a primary key. We will create the table like this: CREATE TABLE( user_ id NUMBER PRIMARY KEY ) Instead of adding the PRIMARY KEY keywords after the data type, we add: CONSTRAINT user_pk PRIMARY KEY Now, we have assigned the name user_pk to this constraint. You can do the same with other constraints, such as UNIQUE. The syntax would be CONSTRAINT username_un UNIQUE. The other way to create constraints requires to put all of our constraints at the bottom of our table creation rather than inline with the column. This type of constraint is known as a table-level constraints. To make a column a primary key using table-level constraints, we add it to the CREATE TABLE command as if it is another row and use the CONSTRAINT keyword to tell Oracle that what is coming is a constraint, not a column in our table. CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR), CONSTRAINT username_un UNIQUE (username), CONSTRAINT users_pk PRIMARY KEY (user_id) ) The primary differences here is that you have to put the column you are talking about in parenthesis after the PRIMARY KEY keyword. That's because it's at the end of the table and you need a way to tell it what column you are talking about. The option of putting it at the end of the table has the added benefit in this situation because if we needed to have a primary key that is the combination of multiple columns, we can do that by just adding the other column in the PRIMARY KEY parenthesis right after a comma. In summary, there are three ways to make constraints. The first is at the column level, unnamed. The second is at the column level, named. The third is at the table level, also named. In the next video we are going to create a named constraint in Oracle SQL Developer, so stay tuned and be sure to subscribe! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 13907 Caleb Curry
Foreign Key in Oracle
 
07:00
Foreign Key in Oracle oracle foreign key WHAT IS A FOREIGN KEY IN ORACLE? 1)A foreign key is a use to make referential integrity in database. 2)Foreign key values in one table must also appear in another table also. 3)The referenced table is called the parent table. 4)Table with the foreign key is called the child table. 5)The foreign key generally reference a primary key in the parent table. CREATE TABLE DEPT --- parent table ( DEPT_ID NUMERIC(10) NOT NULL, EMP_ID NUMERIC(10) NOT NULL, CONSTRAINT DEP_PK PRIMARY KEY (DEPT_ID) ); CREATE TABLE EMPLOYEE -- child table ( EMP_ID NUMERIC(10) NOT NULL, NAME VARCHAR2(50) NOT NULL, CITY VARCHAR2(50), DEPT_NO NUMERIC(10), CONSTRAINT ID_PK PRIMARY KEY (EMP_ID), CONSTRAINT FK_DEP FOREIGN KEY (DEPT_NO) REFERENCES DEPT(DEPT_ID) ); #techquerypond https://techquerypond.wordpress.com https://twitter.com/techquerypond
Views: 424 Tech Query Pond
Part 12   Can we join two tables without primary foreign key relation
 
10:38
Link for all dot net and sql server video tutorial playlists http://www.youtube.com/user/kudvenkat/playlists Link for slides, code samples and text version of the video http://csharp-video-tutorials.blogspot.com/2014/09/part-12-can-we-join-two-tables-without.html Can we join two tables without primary foreign key relation Yes, we can join two tables without primary foreign key relation as long as the column values involved in the join can be converted to one type. ID column in Departments table is not the primary Key and DepartmentId column in Employees table is not the foreign key. But we can still join these tables using ID column from Departments table and DepartmentId column from Employees table, as both the columns involved in the join have same data type i.e int. Select Employees.Name as EmployeeName, Departments.Name as DepartmentName from Employees join Departments on Departments.ID = Employees.DepartmentId The obious next question is, if primary foreign key relation is not mandatory for 2 tables to be joined then what is the use of these keys? Primary key enforces uniqueness of values over one or more columns. Since ID is not a primary key in Departments table, 2 or more departments may end up having same ID value, which makes it impossible to distinguish between them based on the ID column value. Foreign key enforces referential integrity. Without foreign key constraint on DepartmentId column in Employees table, it is possible to insert a row into Employees table with a value for DepartmentId column that does not exist in Departments table. The following insert statement, successfully inserts a new Employee into Employees table whose DepartmentId is 100. But we don't have a department with ID = 100 in Departments table. This means this employee row is an orphan row, and the referential integrity is lost as result Insert into Employees values (8, 'Mary', 'Female', 80000, 100) If we have had a foreign key constraint on DepartmentId column in Employees table, the following insert statement would have failed with the following error. Msg 547, Level 16, State 0, Line 1 The INSERT statement conflicted with the FOREIGN KEY constraint. The conflict occurred in database "Sample", table "dbo.Departments", column 'ID'.
Views: 111131 kudvenkat
Primary key and Foreign Key in DBMS
 
06:11
Primary key vs Foreign key in DBMS. Key concepts in DBMS. (Candidate key, Primary Key, Foreign Key, Alternate Key, Super Key)
Views: 158166 Edu Therapy
Simplest way to create Tables on Oracle 12c
 
04:30
--EMPLOYEE TABLE CREATE TABLE "EMP" ( "EMPNO" NUMBER(4,0), "ENAME" VARCHAR2(10 BYTE), "JOB" VARCHAR2(9 BYTE), "MGR" NUMBER(4,0), "HIREDATE" DATE, "SAL" NUMBER(7,2), "COMM" NUMBER(7,2), "DEPTNO" NUMBER(2,0) ) SEGMENT CREATION IMMEDIATE PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT) TABLESPACE "USERS" ; REM INSERTING into EMP SET DEFINE OFF; Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (5258,'ALEX','MANAGER',null,to_date('25-JAN-89','DD-MON-RR'),1500,500,null); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7875,'Aziz','MANAGER',7839,to_date('17-NOV-97','DD-MON-RR'),5000,1000,10); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7899,'HADI','PRESIDENT',null,to_date('09-MAY-99','DD-MON-RR'),9000,null,10); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (3576,'ABDURAUF','MANAGER',null,null,null,null,null); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (3131,'EBAD','CR',null,to_date('25-JAN-81','DD-MON-RR'),1500,500,null); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7955,'JOHNABRAHM','QWERT',null,to_date('18-JUN-20','DD-MON-RR'),2000,null,30); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (5952,'JENN','MANAGER',null,to_date('25-JAN-81','DD-MON-RR'),1500,500,null); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7369,'SMITH','CLERK',7902,to_date('17-DEC-80','DD-MON-RR'),800,null,20); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7499,'ALLEN','SALESMAN',7698,to_date('20-FEB-81','DD-MON-RR'),1600,300,30); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7521,'WARD','SALESMAN',7698,to_date('22-FEB-81','DD-MON-RR'),1250,500,30); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7566,'JONES','MANAGER',7839,to_date('02-APR-81','DD-MON-RR'),2975,null,20); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7654,'MARTIN','SALESMAN',7698,to_date('28-SEP-81','DD-MON-RR'),1250,1400,30); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7698,'BLAKE','MANAGER',7839,to_date('01-MAY-81','DD-MON-RR'),2850,null,30); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7782,'CLARK','MANAGER',7839,to_date('09-JUN-81','DD-MON-RR'),2450,null,10); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7788,'','ANALYST',7566,to_date('19-APR-87','DD-MON-RR'),3000,null,20); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7839,'KING','PRESIDENT',null,to_date('17-NOV-81','DD-MON-RR'),5000,null,10); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7844,'TURNER','SALESMAN',7698,to_date('08-SEP-81','DD-MON-RR'),1500,0,30); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7876,'ADAMS','CLERK',7788,to_date('23-MAY-87','DD-MON-RR'),1100,null,20); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7900,'JAMES','CLERK',7698,to_date('03-DEC-81','DD-MON-RR'),950,null,30); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7902,'FORD','ANALYST',7566,to_date('03-DEC-81','DD-MON-RR'),3000,null,20); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7934,'MILLER','CLERK',7782,to_date('23-JAN-82','DD-MON-RR'),1300,null,10); Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (5230,'SCARLET','MANAGER',null,to_date('26-JAN-81','DD-MON-RR'),1600,600,null); CREATE UNIQUE INDEX "PK_EMP" ON "EMP" ("EMPNO") PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT) TABLESPACE "USERS" ; ALTER TABLE "EMP" ADD CONSTRAINT "PK_EMP" PRIMARY KEY ("EMPNO") USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT) TABLESPACE "USERS" ENABLE; ALTER TABLE "EMP" ADD CONSTRAINT "FK_DEPTNO" FOREIGN KEY ("DEPTNO") REFERENCES "DEPT" ("DEPTNO") ENABLE;
Views: 51 Fareed Ullah

Supervisor cover letter free examples
Presentation slides cover page
Report background engine
Three little pigs newspaper report format
Is bs psychology a good pre-med course work