How Do I Add a New Column with a Default Value in MySQL?

Adding a New SQL Column with a Default Value

In MySQL, adding a new column to a table with a default value requires the use of the ALTER TABLE statement. The syntax for this statement allows you to specify a default value during column creation.

ALTER TABLE Syntax

The general syntax for adding a new column with a default value is as follows:

ALTER TABLE table_name ADD COLUMN column_name data_type DEFAULT default_value;

In this syntax, table_name represents the table you wish to modify, column_name is the name of the new column, data_type defines the type of data that the column will hold, and default_value specifies the default value for the column.

Example

To add a new column named foo to the table table1 with a default value of 0, you can use the following statement:

ALTER TABLE table1 ADD COLUMN foo INT DEFAULT 0;

Explanation

• ALTER TABLE table1 specifies that we are modifying the table1 table.
• ADD COLUMN foo INT adds a new column named foo with a data type of INT.
• DEFAULT 0 assigns a default value of 0 to the foo column.

Documentation Reference

The syntax provided here is based on the MySQL documentation, which states:

ALTER TABLE tbl_name ADD COLUMN (col_name column_definition,...)

Where column_definition can include a DEFAULT clause:

column_definition:
   data_type [NOT NULL | NULL] [DEFAULT default_value]
   ...

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