ALTER TYPE

Function

ALTER TYPE modifies the definition of a type.

Precautions

Only the type owner or a user granted with the ALTER permission can run the ALTER TYPE command. The system administrator has this permission by default. To modify the owner or schema of a type, you must be a type owner or system administrator and a member of the new owner role.

Syntax

• Modify a type.

  AlterType ::= ALTER TYPE name action [, ... ];

  AlterType ::= ALTER TYPE name OWNER TO { new_owner | CURRENT_USER | SESSION_USER };

  AlterType ::= ALTER TYPE name RENAME ATTRIBUTE attribute_name TO new_attribute_name [ CASCADE | RESTRICT ];

  AlterType ::= ALTER TYPE name RENAME TO new_name;

  AlterType ::= ALTER TYPE name SET SCHEMA new_schema;

  AlterType ::= ALTER TYPE name ADD VALUE [ IF NOT EXISTS ] new_enum_value [ { BEFORE | AFTER } neighbor_enum_value ];

  AlterType ::= ALTER TYPE name RENAME VALUE existing_enum_value TO new_enum_value;

  where action is one of:

  action ::= ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ];

  action ::= DROP ATTRIBUTE [ IF EXISTS ] attribute_name [ CASCADE | RESTRICT ];

  action ::= ALTER ATTRIBUTE attribute_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ CASCADE | RESTRICT ];

• Add a new attribute to a composite type.

  AlterType ::= ALTER TYPE name ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ];

• Delete an attribute from a composite type.

  AlterType ::= ALTER TYPE name DROP ATTRIBUTE [ IF EXISTS ] attribute_name [ CASCADE | RESTRICT ];

• Change the type of an attribute in a composite type.

  AlterType ::= ALTER TYPE name ALTER ATTRIBUTE attribute_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ CASCADE | RESTRICT ];

• Change the owner of a type.

  AlterType ::= ALTER TYPE name OWNER TO { new_owner | CURRENT_USER | SESSION_USER };

• Change the name of a type or the name of an attribute in a composite type.

  AlterType ::= ALTER TYPE name RENAME TO new_name;

  AlterType ::= ALTER TYPE name RENAME ATTRIBUTE attribute_name TO new_attribute_name [ CASCADE | RESTRICT ];

• Move a type to a new schema.

  AlterType ::= ALTER TYPE name SET SCHEMA new_schema;

• Add a new value to an enumerated type.

  AlterType ::= ALTER TYPE name ADD VALUE [ IF NOT EXISTS ] new_enum_value [ { BEFORE | AFTER } neighbor_enum_value ];

• Change an enumerated value in the value list.

  AlterType ::= ALTER TYPE name RENAME VALUE existing_enum_value TO new_enum_value;

Parameter Description

• name

  Specifies the name of an existing type that needs to be modified (optionally schema-qualified).

• new_name

  Specifies the new name of the type.

• new_owner

  Specifies the new owner of the type.

• new_schema

  Specifies the new schema of the type.

• attribute_name

  Specifies the name of the attribute to be added, modified, or deleted.

• new_attribute_name

  Specifies the new name of the attribute to be renamed.

• data_type

  Specifies the data type of the attribute to be added, or the new type of the attribute to be modified.

• new_enum_value

  Specifies a new enumerated value. It is a non-null string with a maximum length of 63 bytes.

• neighbor_enum_value

  Specifies an existing enumerated value before or after which a new enumerated value will be added.

• existing_enum_value

  Specifies an enumerated value to be changed. It is a non-null string with a maximum length of 63 bytes.

• CASCADE

  Determines that the type to be modified, its associated records, and subtables that inherit the type will all be updated.

• RESTRICT

  Refuses to update the associated records of the modified type. This is the default action.

  NOTICE:

  • ADD ATTRIBUTE, DROP ATTRIBUTE, and ALTER ATTRIBUTE can be combined for processing. For example, it is possible to add several attributes or change the types of several attributes at the same time in one command.
  • To modify a schema of a type, you must have the CREATE permission on the new schema. To change the owner, you must be a direct or indirect member of the new owning role, and the member must have the CREATE permission on the schema of this type. (These restrictions enforce that the user can only recreate and delete the type. However, the system administrator can change ownership of any type in any way.) To add an attribute or modify the type of an attribute, you must also have the USAGE permission of this type.

Example

See Examples in CREATE TYPE.

Helpful Links

CREATE TYPE，DROP TYPE