Mysql Add Column Default Value is used to add the default value to the column. The records take a default value when there is no value for a records put inside the specified column of table.
Understand with Example
The Tutorial illustrate an example from 'Mysql Add Column Default Value'. To understand and grasp this example we create a table 'stu' and 'lib' with required fieldnames and datatypes respectively.
Create Table Stu
Create Table Stu(Id int, Name varchar(10), Class int); |
Describe Stu
The Describe Stu is used to describe the fieldname,Type,Null ,etc in the table.
+-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | Id | int(11) | YES | | | | | Name | varchar(10) | YES | | | | | Class | int(11) | YES | | | | +-------+-------------+------+-----+---------+-------+ |
Query for Add Column Default Value
The Query Alter is used to modify the table 'stu' and add a default value of 10 for those records which don't have value specified in a column.
ALTER TABLE Stu MODIFY class int Default '10'; |
Describe Stu
+-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | Id | int(11) | YES | | | | | Name | varchar(15) | YES | | | | | class | int(11) | YES | | 10 | | +-------+-------------+------+-----+---------+-------+ |
Insert data into Stu
Insert Into Stu (Id, Name) values(1,'Komal'); Insert Into Stu (Id, Name) values(2,'Ajay'); Insert Into Stu (Id, Name) values(3,'Rakesh'); Insert Into Stu (Id, Name) values(4,'Bhanu'); Insert Into Stu (Id, Name) values(5,'Santosh'); |
Stu Table
+------+---------+-------+ | Id | Name | class | +------+---------+-------+ | 1 | Komal | 10 | | 2 | Ajay | 10 | | 3 | Rakesh | 10 | | 4 | Bhanu | 10 | | 5 | Santosh | 10 | +------+---------+-------+ |
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