ALTER TABLE¶
Synopsis¶
ALTER TABLE [ IF EXISTS ] name RENAME TO new_name
ALTER TABLE [ IF EXISTS ] name ADD COLUMN [ IF NOT EXISTS ] column_name data_type [ COMMENT comment ] [ WITH ( property_name = expression [, ...] ) ]
ALTER TABLE [ IF EXISTS ] name DROP COLUMN column_name
ALTER TABLE [ IF EXISTS ] name RENAME COLUMN [ IF EXISTS ] column_name TO new_column_name
ALTER TABLE [ IF EXISTS ] name ADD [ CONSTRAINT constraint_name ] { PRIMARY KEY | UNIQUE } ( { column_name [, ...] } ) [ { ENABLED | DISABLED } ] [ [ NOT ] RELY ] [ [ NOT ] ENFORCED } ]
ALTER TABLE [ IF EXISTS ] name DROP CONSTRAINT [ IF EXISTS ] constraint_name
ALTER TABLE [ IF EXISTS ] ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
Description¶
Change the definition of an existing table.
The optional IF EXISTS (when used before the table name) clause causes the error to be suppressed if the table does not exists.
The optional IF EXISTS (when used before the column name) clause causes the error to be suppressed if the column does not exists.
The optional IF NOT EXISTS clause causes the error to be suppressed if the column already exists.
Examples¶
Rename table users to people:
ALTER TABLE users RENAME TO people;
Rename table users to people if table users exists:
ALTER TABLE IF EXISTS users RENAME TO people;
Add column zip to the users table:
ALTER TABLE users ADD COLUMN zip varchar;
Add column zip to the users table if table users exists and column zip not already exists:
ALTER TABLE IF EXISTS users ADD COLUMN IF NOT EXISTS zip varchar;
Drop column zip from the users table:
ALTER TABLE users DROP COLUMN zip;
Drop column zip from the users table if table users and column zip exists:
ALTER TABLE IF EXISTS users DROP COLUMN IF EXISTS zip;
Rename column id to user_id in the users table:
ALTER TABLE users RENAME COLUMN id TO user_id;
Rename column id to user_id in the users table if table users and column id exists:
ALTER TABLE IF EXISTS users RENAME column IF EXISTS id to user_id;
Add constraint pk on column user_id in the users table:
ALTER TABLE users ADD CONSTRAINT pk PRIMARY KEY (user_id);
Add unnamed, disabled unique constraint on columns first_name and last_name in the users table if table users exists:
ALTER TABLE IF EXISTS users ADD UNIQUE (first_name, last_name) DISABLED;
Drop constraint pk from the users table:
ALTER TABLE users DROP CONSTRAINT pk;
Drop constraint pk from the users table if table users exists and constraint pk exists:
ALTER TABLE IF EXISTS users DROP CONSTRAINT IF EXISTS pk;
Add not null constraint to column zip in the users table:
ALTER TABLE users ALTER COLUMN zip SET NOT NULL;
Add not null constraint to column zip in the users table if table users exists:
ALTER TABLE IF EXISTS users ALTER zip SET NOT NULL;
Drop not null constraint from column zip in the users table:
ALTER TABLE users ALTER COLUMN zip DROP NOT NULL;