ADD COLUMN

The ADD COLUMN command is used to add columns to an existing table.

Syntax

The following is the correct syntax for adding a column to an existing table:

alter_table_add_column_statement ::=
    ALTER TABLE [schema_name.]table_name { ADD COLUMN column_def [, ...] }
    ;

table_name ::= identifier

schema_name ::= identifier

column_def :: = { column_name type_name [ default ] [ column_constraint ] }

column_name ::= identifier

column_constraint ::=
    { NOT NULL | NULL }

default ::=
    DEFAULT default_value

Parameters

The following parameters can be used for adding a table:

Parameter	Description
`schema_name`	The schema name for the table. Defaults to `public` if not specified.
`table_name`	The table name to apply the change to.
`ADD COLUMN column_def`	A comma separated list of ADD COLUMN commands
`column_def`	A column definition. A minimal column definition includes a name identifier and a datatype. Other column constraints and default values can be added optionally.

Usage Notes

The following usage notes apply when adding a column to an existing table:

When adding a new column to an existing table, a default (or null constraint) has to be specified, even if the table is empty.

New columns you add to the table cannot be TEXT or contain an IDENTITY.

Examples

The Examples section includes the following examples:

Adding a Simple Column with a Default Value 

This example shows how to add a simple column with a default value:

ALTER TABLE cool_animals
  ADD COLUMN number_of_eyes INT DEFAULT 2 NOT NULL;

Adding Several Columns in One Command 

This example shows how to add several columns in one command:

ALTER TABLE cool_animals
  ADD COLUMN number_of_eyes INT DEFAULT 2 NOT NULL,
  ADD COLUMN date_seen DATE DEFAULT '2019-08-01';

Permissions

The role must have the DDL permission at the database or table level.