Add new column in sql

To add a new column in SQL, you can use the ALTER TABLE statement with the ADD COLUMN clause. The syntax is as follows:

ALTER TABLE table_name
ADD COLUMN new_column_name data_type;

Here:

• table_name is the name of the table you want to modify.
• new_column_name is the name of the new column you want to add.
• data_type is the data type of the new column (e.g. INT, VARCHAR, DATE, etc.).

For example, to add a new column called age with a data type of INT to a table called employees, you would use the following SQL statement:

ALTER TABLE employees
ADD COLUMN age INT;

This will add a new column called age with a data type of INT to the employees table.

You can also specify additional options, such as:

• NULL or NOT NULL to specify whether the column can contain null values.
• DEFAULT to specify a default value for the column.
• UNIQUE or PRIMARY KEY to specify that the column is unique or a primary key.

For example:

ALTER TABLE employees
ADD COLUMN age INT NOT NULL DEFAULT 0;

This will add a new column called age with a data type of INT, not null, and a default value of 0.

Note that you can only add a new column to a table that is not currently being used by a query or transaction. If you try to add a new column to a table that is being used, you will get an error.

Also, some databases like MySQL, PostgreSQL, and SQLite support adding a new column with a default value using the ALTER TABLE statement with the ADD COLUMN clause, but some databases like Oracle and Microsoft SQL Server require you to use the ALTER TABLE statement with the MODIFY clause instead.