How to Add a Column to a Table in SQL

You can add a new column to an existing table using the ALTER TABLE statement with the ADD clause.

Syntax:

ALTER TABLE table_nameADD column_name data_type [column_constraints];

• column_name: Name of the new column.

• data_type: Data type for the new column (e.g., INT, VARCHAR(50), DATE).

• [column_constraints]: Optional constraints like NOT NULL, DEFAULT, etc.

Examples:

1. Add a simple column

ALTER TABLE employeesADD phone_number VARCHAR(15);

2. Add a column with constraints and default value

ALTER TABLE employeesADD status VARCHAR(10) NOT NULL DEFAULT 'active';

Notes:

• Some databases allow adding multiple columns in one statement (e.g., MySQL):

ALTER TABLE employeesADD (city VARCHAR(50), postal_code VARCHAR(10));

• Be careful when adding NOT NULL columns to tables with existing data; you may need to specify a DEFAULT value or allow NULL temporarily.

If you want syntax for a particular SQL database or have more questions, feel free to ask!