SQL PRIMARY KEY Constraint

This page discusses - SQL PRIMARY KEY Constraint

SQL PRIMARY KEY Constraint

SQL PRIMARY KEY Constraint

     

The PRIMARY KEY constraint is used to uniquely identifies each record in a database table. The Primary keys in a table contains a unique values. It should contain NULL values. The Table contain a primary key and each table have only primary key.

Understand with Example

The Tutorial illustrate an example to understand SQL PRIMARY KEY Constraint. In this example, we create a table 'Stu_Class_10.The create  statement is used to create a table 'Stu_Class_10'.The following SQL creates a PRIMARY KEY on the "Stu_Id" when the" Stu_Class_10" table is created.

Create Table Stu_Class_10

 

 

 

create table Stu_Class_10(
Stu_Id integer(2) NOT NULL,
Stu_Name varchar(15),
Stu_Class  varchar(10),
PRIMARY KEY(Stu_Id))

Insert data into Stu_Class_10

The insert into statement is used to add the records or rows to the table 'Stu_Class_10'. 

insert into Stu_Class_10 values(1,'Komal',10)
insert into Stu_Class_10 values(2,'Ajay',10)
insert into Stu_Class_10 values(3,'Rakesh',10)
insert into Stu_Class_10 values(4,'Bhanu',10)
insert into Stu_Class_10 values(5,'Santosh',10)

Stu_Class_10

Stu_Id Stu_Name Stu_Class
1 Komal 10
2 Ajay 10
3 Rakesh 10
4 Bhanu 10
5 Santosh 10

Tutorials

  1. Quartz Tutorial
  2. Introduction to Quartz Scheduler
  3. Download Quartz Job Scheduler
  4. Hello World Quartz Scheduler
  5. Jobs & Triggers
  6. More About Triggers
  7. More About Simple Trigger
  8. More About the CronTrigger
  9. Example of Cron Trigger
  10. Implementing more than one Job Details and Triggers
  11. Scheduler Shutdown Example
  12. TriggerListeners and JobListeners
  13. JobStores
  14. Configuration, Resource Usage and StdSchedulerFactory
  15. Establish a Connection with MySQL Database
  16. Advance (Enterprise) Features
  17. Quartz Tutorial
  18. Aggregate Functions in SQL, SQL Tutorial
  19. Backup File With Separator
  20. Backup Into txt File
  21. Backup selected records into txt file
  22. Call Procedure
  23. Close Cursors in SQL
  24. Create After Insert Trigger in SQL
  25. Create Before Insert Trigger in SQL
  26. Create Before Update Trigger in SQL
  27. Create Delete Trigger in SQL
  28. Create a Simple Procedure
  29. Create After Update Trigger in SQL
  30. Create Database in SQL,SQL Tutorial
  31. Creating Cursors in SQL
  32. Declare Cursors in SQL
  33. The DELETE Statement, SQL Tutorial
  34. SQL SELECT DISTINCT Statement
  35. Drop Index
  36. Drop Table
  37. Close Cursors in SQL
  38. Use HANDLER Statement in Cursors
  39. Insert Data From File
  40. The INSERT INTO Statement, SQL Tutorial