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SQL Alter Table Primary Key

                         

Alter a Table Primary Key in SQL modifies the existing table and adds a primary key.

Create Table Stu_Table

SQL statement to create table:

create table Stu_Table(Stu_Id varchar(2), Stu_Name varchar(15), Stu_Class  varchar(10))

Insert data into Stu_Table

SQL statement to insert data into table:

insert into Stu_Table values(1,'Komal',10);
insert into Stu_Table values(2,'Ajay',10);
insert into Stu_Table values(3,'Rakesh',10);
insert into Stu_Table values(4,'Bhanu',10);
insert into Stu_Table values(5,'Santosh',10);
insert into Stu_Table values(6,'Tanuj',10);

Stu_Table

Records in the table:

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

Describe Stu_Table

+-----------+-------------+------+-----+---------+-------+
| Field     | Type        | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| Stu_Id    | varchar(2)  | NO   |     |         |       |
| Stu_Name  | varchar(15) | YES  |     |         |       |
| stu_class | varchar(10) | NO   |     |         |       |
+-----------+-------------+------+-----+---------+-------+

Alter Table Primary Key  Syntax

The table_name is the name of the table on which primary key is added.

The  column_name is the name of the column on which primary key is created.

ALTER TABLE table_name 
ADD PRIMARY KEY (column_name)

Alter Table Primary Key Query

The given Query show you an example to alter a table name 'Stu_Table' on which primary key is added. The 'Stu_Id' is the name of the column on which primary key is created.  

ALTER TABLE Stu_Table
ADD PRIMARY KEY (Stu_Id)

Describe Stu_Table

+-----------+-------------+------+-----+---------+-------+
| Field     | Type        | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| Stu_Id    | varchar(2)  | NO   | PRI |         |       |
| Stu_Name  | varchar(15) | YES  |     |         |       |
| stu_class | varchar(10) | NO   |     |         |       |
+-----------+-------------+------+-----+---------+-------+

                         

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