Purpose

Use the ALTER DIMENSION statement to change the hierarchical relationships or dimension attributes of a dimension.

Prerequisites

The dimension must be in your schema or you must have the ALTER ANY DIMENSION system privilege to use this statement.

A dimension is always altered under the rights of the owner.

Syntax

alter_dimension::=

Description of the illustration alter_dimension.eps

(level_clause::=, hierarchy_clause::=, attribute_clause::=, extended_attribute_clause::=)

level_clause::=

Description of the illustration level_clause.eps

hierarchy_clause::=

Description of the illustration hierarchy_clause.eps

(dimension_join_clause::=)

dimension_join_clause::=

Description of the illustration dimension_join_clause.eps

attribute_clause::=

Description of the illustration attribute_clause.eps

extended_attribute_clause::=

Description of the illustration extended_attribute_clause.eps

Semantics

The following keywords, parameters, and clauses have meaning unique to ALTER DIMENSION. Keywords, parameters, and clauses that do not appear here have the same functionality that they have in the CREATE DIMENSION statement. Refer to CREATE DIMENSION for more information.

schema

Specify the schema of the dimension you want to modify. If you do not specify schema, then Oracle Database assumes the dimension is in your own schema.

dimension

Specify the name of the dimension. This dimension must already exist.

ADD

The ADD clauses let you add a level, hierarchy, or attribute to the dimension. Adding one of these elements does not invalidate any existing materialized view.

Oracle Database processes ADD LEVEL clauses prior to any other ADD clauses.

DROP

The DROP clauses let you drop a level, hierarchy, or attribute from the dimension. Any level, hierarchy, or attribute you specify must already exist.

Within one attribute, you can drop one or more level-to-column relationships associated with one level.

Restriction on DROP

If any attributes or hierarchies reference a level, then you cannot drop the level until you either drop all the referencing attributes and hierarchies or specify CASCADE.

CASCADE

Specify CASCADE if you want Oracle Database to drop any attributes or hierarchies that reference the level, along with the level itself.

RESTRICT

Specify RESTRICT if you want to prevent Oracle Database from dropping a level that is referenced by any attributes or hierarchies. This is the default.

COMPILE

Specify COMPILE to explicitly recompile an invalidated dimension. Oracle Database automatically compiles a dimension when you issue an ADD clause or DROP clause. However, if you alter an object referenced by the dimension (for example, if you drop and then re-create a table referenced in the dimension), Oracle Database invalidates, and you must recompile it explicitly.

Examples

Modifying a Dimension: Examples

The following examples modify the customers_dim dimension in the sample schema sh:

ALTER DIMENSION customers_dim
   DROP ATTRIBUTE country;

ALTER DIMENSION customers_dim
   ADD LEVEL zone IS customers.cust_postal_code
   ADD ATTRIBUTE zone DETERMINES (cust_city);