ALTER TABLE

    The optional (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.

    1. ALTER TABLE users RENAME TO people;

    Rename table users to people if table users exists:

      Add column zip to the table:

      Add column zip to the users table if table users exists and column zip not already exists:

      1. ALTER TABLE IF EXISTS users ADD COLUMN IF NOT EXISTS zip varchar;
      1. ALTER TABLE users DROP COLUMN zip;

      Drop column zip from the users table if table and column zip exists:

      Rename column id to user_id in the users table:

        Rename column id to user_id in the users table if table users and column id exists: