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))
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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)
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Stu_Class_10
| Stu_Id |
Stu_Name |
Stu_Class |
| 1 |
Komal |
10 |
| 2 |
Ajay |
10 |
| 3 |
Rakesh |
10 |
| 4 |
Bhanu |
10 |
| 5 |
Santosh |
10 |

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