FirebirdSQL logo
 DOMAININDEX 

The ALTER [COLUMN] Clause

With the ALTER [COLUMN] clause, attributes of existing columns can be modified without the need to drop and re-add the column.Permitted modifications are:

  • change the name (does not affect the metadata change counter)

  • change the data type (increases the metadata change counter by one)

  • change the column position in the column list of the table (does not affect the metadata change counter)

  • delete the default column value (does not affect the metadata change counter)

  • set a default column value or change the existing default (does not affect the metadata change counter)

  • change the type and expression for a computed column (does not affect the metadata change counter)

  • set the NOT NULL constraint (does not affect the metadata change counter)

  • drop the NOT NULL constraint (does not affect the metadata change counter)

  • change the type of an identity column, or change an identity column to a regular column

  • restart an identity column

  • change the increment of an identity column

Renaming a Column: the TO Clause

The TO keyword with a new identifier renames an existing column.The table must not have an existing column that has the same identifier.

It will not be possible to change the name of a column that is included in any constraint: primary key, unique key, foreign key, or CHECK constraints of the table.

Renaming a column will also be disallowed if the column is used in any stored PSQL module or view.