ALTER TYPE Statement

The ALTER TYPE statement does one of the following to a type that was created with "CREATE TYPE Statement" and "CREATE TYPE BODY Statement":

• Evolves the type; that is, adds or drops member attributes or methods.

  For more information about type evolution, see Oracle Database Object-Relational Developer's Guide.

• Changes the specification of the type by adding object member subprogram specifications.

• Recompiles the specification or body of the type.

• Resets the version of the type to 1, so that it is no longer considered to be evolved.

Topics:

• Prerequisites

• Syntax

• Semantics

• Examples

• Related Topics

Prerequisites

If the type is in the SYS schema, you must be connected as SYSDBA. Otherwise, the type must be in your own schema and you must have CREATE TYPE or CREATE ANY TYPE system privilege, or you must have ALTER ANY TYPE system privileges.

Syntax

alter_type::=

Description of the illustration alter_type.gif

See:

• alter_attribute_definition::=

• alter_method_spec::=

• alter_collection_clauses::=

• compile_type_clause::=

• dependent_handling_clause::=

• replace_type_clause::=

compile_type_clause::=

Description of the illustration compile_type_clause.gif

compiler_parameters_clause::=

Description of the illustration compiler_parameters_clause.gif

replace_type_clause::=

Description of the illustration replace_type_clause.gif

invoker_rights_clause::=

Description of the illustration invoker_rights_clause.gif

element_spec::=

Description of the illustration element_spec.gif

(inheritance_clauses::=, subprogram_spec::=, constructor_spec::=, map_order_function_spec::=, pragma_clause::=)

inheritance_clauses::=

Description of the illustration inheritance_clauses.gif

subprogram_spec::=

Description of the illustration subprogram_spec.gif

(procedure_spec::=, function_spec::=)

procedure_spec::=

Description of the illustration procedure_spec.gif

function_spec::=

Description of the illustration function_spec.gif

constructor_spec::=

Description of the illustration constructor_spec.gif

map_order_function_spec::=

Description of the illustration map_order_function_spec.gif

(function_spec::=)

pragma_clause::=

Description of the illustration pragma_clause.gif

alter_method_spec::=

Description of the illustration alter_method_spec.gif

(map_order_function_spec::=, subprogram_spec::=)

alter_attribute_definition::=

Description of the illustration alter_attribute_definition.gif

alter_collection_clauses::=

Description of the illustration alter_collection_clauses.gif

dependent_handling_clause::=

Description of the illustration dependent_handling_clause.gif

exceptions_clause::=

Description of the illustration exceptions_clause.gif

Semantics

schema

The name of the schema containing the type. The default is your own schema.

type

The name of an ADT, varray type, or nested table type.

Restriction on type You cannot evolve an editioned ADT.

The ALTER TYPE statement fails with ORA-22348 if either of the following is true:

• type is an editioned ADT and the ALTER TYPE statement has no compile_type_clause.

  (You can use the ALTER TYPE statement to recompile an editioned object type, but not for any other purpose.)

• type has a dependent that is an editioned ADT and the ALTER TYPE statement has a CASCADE clause.

An editioned object is a schema object that has an editionable object type and was created by a user for whom editions are enabled. For more information about editioned objects, see Oracle Database Advanced Application Developer's Guide.

compile_type_clause

Recompiles the type specification and body. This is the default if neither SPECIFICATION nor BODY is specified.

During recompilation, the database drops all persistent compiler switch settings, retrieves them again from the session, and stores them after compilation. To avoid this process, specify the REUSE SETTINGS clause.

If recompiling the type results in compilation errors, then the database returns an error and the type remains invalid. You can see the associated compiler error messages with the SQL*Plus command SHOW ERRORS.

DEBUG

Has the same behavior for a type as it does for a function. See DEBUG.

SPECIFICATION

Recompiles only the type specification.

BODY

Recompiles only the type body.

compiler_parameters_clause

Has the same behavior for a type as it does for a function. See the ALTER FUNCTION compiler_parameters_clause.

REUSE SETTINGS

Has the same behavior for a type as it does for a function. See REUSE SETTINGS.

replace_type_clause

Adds member subprogram specifications.

Restriction on replace_type_clause

This clause is valid only for ADTs, not for nested tables or varrays.

attribute

The name of an object attribute. Attributes are data items with a name and a type specifier that form the structure of the object.

element_spec

The elements of the redefined object.

inheritance_clauses

Specifies the relationship between supertypes and subtypes.

subprogram_spec

The MEMBER and STATIC clauses let you specify for the ADT a function or procedure subprogram which is referenced as an attribute.

You must specify a corresponding method body in the ADT body for each procedure or function specification.

procedure_spec

The specification of a procedure subprogram.

function_spec

The specification of a function subprogram.

pragma_clause

Denies member functions read/write access to database tables, packaged variables, or both, and thereby helps to avoid side effects.

Restriction on pragma_clause The pragma_clause is not valid when dropping a method.

map_order_function_spec

You can declare either one MAP method or one ORDER method, regardless how many MEMBER or STATIC methods you declare. However, a subtype can override a MAP method if the supertype defines a NOT FINAL MAP method. If you declare either method, then you can compare object instances in SQL.

If you do not declare either method, then you can compare object instances only for equality or inequality. Instances of the same type definition are equal only if each pair of their corresponding attributes is equal. No comparison method must be specified to determine the equality of two ADTs.

• For MAP, specify a member function (MAP method) that returns the relative position of a given instance in the ordering of all instances of the object. A map method is called implicitly and induces an ordering of object instances by mapping them to values of a predefined scalar type. The database uses the ordering for comparison conditions and ORDER BY clauses.

  If type will be referenced in queries involving sorts (through ORDER BY, GROUP BY, DISTINCT, or UNION clauses) or joins, and you want those queries to be parallelized, then you must specify a MAP member function.

  If the argument to the MAP method is null, then the MAP method returns null and the method is not invoked.

  An object specification can contain only one MAP method, which must be a function. The result type must be a predefined SQL scalar type, and the MAP function can have no arguments other than the implicit SELF argument.

  A subtype cannot define a new MAP method, but it can override an inherited MAP method.

• For ORDER, specify a member function (ORDER method) that takes an instance of an object as an explicit argument and the implicit SELF argument and returns either a negative, zero, or positive integer. The negative, zero, or positive value indicates that the implicit SELF argument is less than, equal to, or greater than the explicit argument.

  If either argument to the ORDER method is null, then the ORDER method returns null and the method is not invoked.

  When instances of the same ADT definition are compared in an ORDER BY clause, the ORDER method function is invoked.

  An object specification can contain only one ORDER method, which must be a function having the return type NUMBER.

  A subtype cannot define an ORDER method, nor can it override an inherited ORDER method.

invoker_rights_clause

Specifies the AUTHID property of the member functions and procedures of the ADT. For information about the AUTHID property, see "Invoker's Rights and Definer's Rights (AUTHID Property)".

Restriction on invoker_rights_clause You can specify this clause only for an ADT, not for a nested table or varray.

alter_method_spec

Adds a method to or drops a method from type. The database disables any function-based indexes that depend on the type.

In one ALTER TYPE statement you can add or drop multiple methods, but you can reference each method only once.

ADD

When you add a method, its name must not conflict with any existing attributes in its type hierarchy.

DROP

When you drop a method, the database removes the method from the target type.

Restriction on DROP You cannot drop from a subtype a method inherited from its supertype. Instead you must drop the method from the supertype.

subprogram_spec

The MEMBER and STATIC clauses let you add a procedure subprogram to or drop it from the ADT.

Restriction on subprogram_spec You cannot define a STATIC method on a subtype that redefines a MEMBER method in its supertype, or vice versa.

map_order_function_spec

If you declare either a MAP or ORDER method, then you can compare object instances in SQL.

Restriction on map_order_function_spec You cannot add an ORDER method to a subtype.

alter_attribute_definition

Adds, drops, or modifies an attribute of an ADT. In one ALTER TYPE statement, you can add, drop, or modify multiple member attributes or methods, but you can reference each attribute or method only once.

ADD ATTRIBUTE

The name of the attribute must not conflict with existing attributes or methods in the type hierarchy. The database adds the attribute to the end of the locally defined attribute list.

If you add the attribute to a supertype, then it is inherited by all of its subtypes. In subtypes, inherited attributes always precede declared attributes. Therefore, you might need to update the mappings of the implicitly altered subtypes after adding an attribute to a supertype.

DROP ATTRIBUTE

When you drop an attribute from a type, the database drops the column corresponding to the dropped attribute and any indexes, statistics, and constraints referencing the dropped attribute.

You need not specify the data type of the attribute you are dropping.

Restrictions on DROP ATTRIBUTE 

• You cannot drop an attribute inherited from a supertype. Instead you must drop the attribute from the supertype.

• You cannot drop an attribute that is part of a partitioning, subpartitioning, or cluster key.

• You cannot drop an attribute of a primary-key-based object identifier of an object table or a primary key of an index-organized table.

• You cannot drop all of the attributes of a root type. Instead you must drop the type. However, you can drop all of the locally declared attributes of a subtype.

MODIFY ATTRIBUTE

Modifies the data type of an existing scalar attribute. For example, you can increase the length of a VARCHAR2 or RAW attribute, or you can increase the precision or scale of a numeric attribute.

Restriction on MODIFY ATTRIBUTE You cannot expand the size of an attribute referenced in a function-based index, domain index, or cluster key.

[NOT] FINAL

Indicates whether any further subtypes can be created for this type:

• Specify FINAL if no further subtypes can be created for this type.

• Specify NOT FINAL if further subtypes can be created under this type.

If you change the property between FINAL and NOT FINAL, then you must specify the CASCADE clause of the dependent_handling_clause to convert data in dependent columns and tables.

• If you change a type from NOT FINAL to FINAL, then you must specify CASCADE [INCLUDING TABLE DATA]. You cannot defer data conversion with CASCADE NOT INCLUDING TABLE DATA.

• If you change a type from FINAL to NOT FINAL, then:

  • Specify CASCADE INCLUDING TABLE DATA to create substitutable tables and columns of that type, but you are not concerned about the substitutability of the existing dependent tables and columns. The database marks all existing dependent columns and tables NOT SUBSTITUTABLE AT ALL LEVELS, so you cannot insert the subtype instances of the altered type into these existing columns and tables.

  • Specify CASCADE CONVERT TO SUBSTITUTABLE to create substitutable tables and columns of the type and also store subtype instances of the altered type in existing dependent tables and columns. The database marks all existing dependent columns and tables SUBSTITUTABLE AT ALL LEVELS except those that are explicitly marked NOT SUBSTITUTABLE AT ALL LEVELS.

    See Also:

    Oracle Database Object-Relational Developer's Guide for a full discussion of ADT evolution

Restriction on FINAL You cannot change a user-defined type from NOT FINAL to FINAL if the type has any subtypes.

[NOT] INSTANTIABLE

Indicates whether any object instances of this type can be constructed:

• Specify INSTANTIABLE if object instances of this type can be constructed.

• Specify NOT INSTANTIABLE if no constructor (default or user-defined) exists for this type. You must specify these keywords for any type with noninstantiable methods and for any type that has no attributes (either inherited or specified in this statement).

Restriction on NOT INSTANTIABLE You cannot change a user-defined type from INSTANTIABLE to NOT INSTANTIABLE if the type has any table dependents.

RESET

Resets the version of this type to 1, so that it is no longer considered to be evolved.

RESET is intended for evolved ADTs that are preventing their owners from being editions-enabled. For information about enabling editions for users, see Oracle Database Advanced Application Developer's Guide.

To see the version number of an ADT, select VERSION# from the static data dictionary view *_TYPE_VERSIONS. For example:

SELECT Version# FROM DBA_TYPE_VERSIONS
WHERE Owner = schema
AND Name = 'type_name'
AND Type = 'TYPE'

For an evolved ADT, the preceding query returns multiple rows with different version numbers. RESET deletes every row whose version number is less than the maximum version number, and resets the version number of the remaining rows to 1—see "Evolving and Resetting an ADT: Example".

Restriction on RESET You cannot specify RESET if the type has any table dependents (direct or indirect).

alter_collection_clauses

These clauses are valid only for collection types.

MODIFY LIMIT integer

Increases the number of elements in a varray. It is not valid for nested tables. Specify an integer greater than the current maximum number of elements in the varray.

ELEMENT TYPE datatype

Increases the precision, size, or length of a scalar data type of a varray or nested table. This clause is not valid for collections of ADTs.

• For a collection of NUMBER, you can increase the precision or scale.

• For a collection of RAW, you can increase the maximum size.

• For a collection of VARCHAR2 or NVARCHAR2, you can increase the maximum length.

  See Also:

  "Increasing the Length of a Collection Type: Example"

dependent_handling_clause

Specifies how the database is to handle objects that are dependent on the modified type. If you omit this clause, then the ALTER TYPE statement terminates if type has any dependent type or table.

INVALIDATE

Invalidates all dependent objects without any checking mechanism.

CASCADE

Propagates the type change to dependent types and tables. The database terminates the statement if any errors are found in the dependent types or tables unless you also specify FORCE.

If you change the property of the type between FINAL and NOT FINAL, then you must specify this clause to convert data in dependent columns and tables. See "[NOT] FINAL".

INCLUDING TABLE DATA

Converts data stored in all user-defined columns to the most recent version of the column type. This is the default.

• For each attribute added to the column type, the database adds an attribute to the data and initializes it to null.

• For each attribute dropped from the referenced type, the database removes the corresponding attribute data from each row in the table.

If you specify INCLUDING TABLE DATA, then all of the tablespaces containing the table data must be in read/write mode.

If you specify NOT INCLUDING TABLE DATA, then the database upgrades the metadata of the column to reflect the changes to the type but does not scan the dependent column and update the data as part of this ALTER TYPE statement. However, the dependent column data remains accessible, and the results of subsequent queries of the data reflect the type modifications.

CONVERT TO SUBSTITUTABLE

Specify this clause if you are changing the type from FINAL to NOT FINAL and you want to create substitutable tables and columns of the type and also store subtype instances of the altered type in existing dependent tables and columns. See "[NOT] FINAL" for more information.

exceptions_clause

Specify FORCE if you want the database to ignore the errors from dependent tables and indexes and log all errors in the specified exception table. The exception table must have been created by running the DBMS_UTILITY.CREATE_ALTER_TYPE_ERROR_TABLE procedure.

Examples

Adding a Member Function: Example This example uses the ADT data_typ1. See "ADT Examples" for the example that creates this ADT. A method is added to data_typ1 and its type body is modified to correspond. The date formats are consistent with the order_date column of the oe.orders sample table:

ALTER TYPE data_typ1 
   ADD MEMBER FUNCTION qtr(der_qtr DATE) 
   RETURN CHAR CASCADE;

CREATE OR REPLACE TYPE BODY data_typ1 IS 
  MEMBER FUNCTION prod (invent NUMBER) RETURN NUMBER IS 
  BEGIN 
  RETURN (year + invent); 
  END; 
     MEMBER FUNCTION qtr(der_qtr DATE) RETURN CHAR IS 
     BEGIN 
       IF (der_qtr < TO_DATE('01-APR', 'DD-MON')) THEN 
         RETURN 'FIRST'; 
       ELSIF (der_qtr < TO_DATE('01-JUL', 'DD-MON')) THEN 
         RETURN 'SECOND'; 
       ELSIF (der_qtr < TO_DATE('01-OCT', 'DD-MON')) THEN 
         RETURN 'THIRD'; 
       ELSE 
         RETURN 'FOURTH'; 
       END IF; 
     END; 
   END;
/

Adding a Collection Attribute: Example This example adds the author attribute to the textdoc_tab object column of the text table. See "ADT Examples" for the example that creates the underlying textdoc_typ type.

CREATE TABLE text (
   doc_id       NUMBER,
   description  textdoc_tab)
   NESTED TABLE description STORE AS text_store;

ALTER TYPE textdoc_typ 
   ADD ATTRIBUTE (author VARCHAR2) CASCADE;

The CASCADE keyword is required because both the textdoc_tab and text table are dependent on the textdoc_typ type.

Increasing the Number of Elements of a Collection Type: Example This example increases the maximum number of elements in the varray phone_list_typ_demo. See "ADT Examples" for the example that creates this type.

ALTER TYPE phone_list_typ_demo
  MODIFY LIMIT 10 CASCADE;

Increasing the Length of a Collection Type: Example This example increases the length of the varray element type phone_list_typ:

ALTER TYPE phone_list_typ
  MODIFY ELEMENT TYPE VARCHAR(64) CASCADE;

Recompiling a Type: Example This example recompiles type cust_address_typ in the hr schema:

ALTER TYPE cust_address_typ2 COMPILE;

Recompiling a Type Specification: Example This example compiles the type specification of link2.

CREATE TYPE link1 AS OBJECT
  (a NUMBER); 
/
CREATE TYPE link2 AS OBJECT
  (a NUMBER, 
   b link1, 
   MEMBER FUNCTION p(c1 NUMBER) RETURN NUMBER); 
/
CREATE TYPE BODY link2 AS
   MEMBER FUNCTION p(c1 NUMBER) RETURN NUMBER IS 
      BEGIN  
         dbms_output.put_line(c1);
         RETURN c1; 
      END; 
   END; 
/

In this example, both the specification and body of link2 are invalidated because link1, which is an attribute of link2, is altered.

ALTER TYPE link1 ADD ATTRIBUTE (b NUMBER) INVALIDATE;

You must recompile the type by recompiling the specification and body in separate statements:

ALTER TYPE link2 COMPILE SPECIFICATION;
         
ALTER TYPE link2 COMPILE BODY;
         

Alternatively, you can compile both specification and body at the same time:

ALTER TYPE link2 COMPILE;

Evolving and Resetting an ADT: Example This example creates an ADT in the schema Usr, evolves that ADT, and then tries to enable editions for Usr, which fails. Then the example resets the version of the ADT to 1 and succeeds in enabling editions for Usr. To show the version numbers of the newly created, evolved, and reset ADT, the example uses the static data dictionary view DBA_TYPE_VERSIONS.

-- Create ADT in schema Usr:
create type Usr.My_ADT authid Definer is object(a1 number)

-- Show version number of ADT:
select Version#||Chr(10)||Text t
from DBA_Type_Versions
where Owner = 'USR'
and Type_Name = 'MY_ADT'
/

Result:

T
--------------------------------------------------------------------------------
1
type     My_ADT authid Definer is object(a1 number)


1 row selected.

-- Evolve ADT:
alter type Usr.My_ADT add attribute (a2 number)
/

-- Show version number of evolved ADT:
select Version#||Chr(10)||Text t
from DBA_Type_Versions
where Owner = 'USR'
and Type_Name = 'MY_ADT'
/

Result:

T
--------------------------------------------------------------------------------
1
type     My_ADT authid Definer is object(a1 number)

2
type     My_ADT authid Definer is object(a1 number)

2
 alter type     My_ADT add attribute (a2 number)


3 rows selected.

-- Try to enable editions for Usr:
alter user Usr enable editions
/

Result:

alter user Usr enable editions
*
ERROR at line 1:
ORA-38820: user has evolved object type

-- Reset version of ADT to 1:
alter type Usr.My_ADT reset
/

-- Show version number of reset ADT:
select Version#||Chr(10)||Text t
from DBA_Type_Versions
where Owner = 'USR'
and Type_Name = 'MY_ADT'
/

Result:

T
--------------------------------------------------------------------------------
1
type     My_ADT authid Definer is object(a1 number)

1
 alter type     My_ADT add attribute (a2 number)


2 rows selected.

-- Try to enable editions for Usr:
alter user Usr enable editions
/

Result:

User altered.

Related Topics

• "CREATE TYPE Statement"

• "CREATE TYPE BODY Statement"

• "DROP TYPE Statement"