SQL Alter Column Default Value

Alter Column Default Value in  SQL Server is used with Create Table Statement. The default value will be set as per specified column. The use of default value is specified when insert is performed, but value in the column is not set.

Understand with Example 

In this Tutorial, the query create a table 'Stu_Table' using a create statement. The insert into in SQL Query add the records to table. The Describe table show you the Table attribute like field, data type etc.

Create Table Stu_Table

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

Insert data into Stu_Table

insert into Stu_Table (Stu_Id, Stu_Name) values(1,'Komal');
insert into Stu_Table (Stu_Id, Stu_Name) values(2,'Ajay');
insert into Stu_Table (Stu_Id, Stu_Name) values(3,'Rakesh');
insert into Stu_Table (Stu_Id, Stu_Name) values(4,'Bhanu');
insert into Stu_Table (Stu_Id, Stu_Name) values(5,'Santosh');

Stu_Table

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

Describe Stu_Table

+-----------+-------------+------+-----+---------+-------+
| Field     | Type        | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| Stu_Id    | varchar(10) | YES  |     |         |       |
| Stu_Name  | varchar(10) | YES  |     | NULL    |       |
| Stu_Class | varchar(5)  | YES  |     | NULL    |       |
+-----------+-------------+------+-----+---------+-------+

Alter column Column Default Query

The Alter Table Keywords modify table'Stu_Table' and MODIFY keyword modify the data type of field Stu_Id (varchar(10)) to Stu_Id(int(3)) and set the default value for this field is set '10'.Whenever you leave a blank value in Stu_Id, This field would take default value of '10'.

ALTER TABLE Stu_Table MODIFY Stu_Id int(3) Default '10'

Describe Stu_Table

+-----------+--------------+------+-----+---------+-------+
| Field     | Type         | Null | Key | Default | Extra |
+-----------+--------------+------+-----+---------+-------+
| Stu_Id    | int(3)       | No   |     |  10       |       |
| Stu_Name  | varchar(10)  | YES  |     | NULL    |       |
| Stu_Class | varchar(5)   | YES  |     | NULL     |       |
+-----------+--------------+------+-----+---------+-------+

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