Example 1: Deleting a domain not referred to by columns

    SQL> --
    SQL> -- The following CREATE DOMAIN statement creates a domain
    SQL> -- that is not used by any columns:
    SQL> --
    SQL> CREATE DOMAIN ABCD IS CHAR(4);
    SQL> --
    SQL> -- The SHOW DOMAINS statement shows domain ABCD at the
    SQL> -- top of the list:
    SQL> --
    SQL> SHOW DOMAINS

    User domains in database with filename personnel
    ABCD                            CHAR(4)
    ADDRESS_DATA_1_DOM              CHAR(25)
    ADDRESS_DATA_2_DOM              CHAR(20)
       .
       .
       .

    SQL> --
    SQL> -- Now delete the domain:
    SQL> --
    SQL> DROP DOMAIN ABCD;
    SQL> --
    SQL> -- The SHOW DOMAINS statement shows that the
    SQL> -- domain ABCD has been deleted:
    SQL> --
    SQL> SHOW DOMAINS

    User domains in database with filename personnel
    ADDRESS_DATA_1_DOM              CHAR(25)
    ADDRESS_DATA_2_DOM              CHAR(20)
       .
       .
       .

    Example 2: Deleting a domain referred to by columns

    The following example deletes a domain definition. Because a
    column refers to the domain definition and a constraint refers
    to the column, you must first alter the table before deleting the
    domain.

    SQL> --
    SQL> -- Attempt to delete the domain SEX_DOM.  Error messages
    SQL> -- indicate that the table EMPLOYEES uses the domain
    SQL> -- SEX_DOM, so SEX_DOM cannot yet be deleted:
    SQL> --
    SQL> DROP DOMAIN SEX_DOM;
    %RDB-E-NO_META_UPDATE, metadata update failed
    -RDMS-F-RELEXI, field SEX_DOM is used in relation EMPLOYEES
    -RDMS-F-FLDNOTDEL, field SEX_DOM has not been deleted
    SQL> --
    SQL> -- Looking at the EMPLOYEES table shows that SEX is the
    SQL> -- column that depends on the domain SEX_DOM.  Try
    SQL> -- to delete the column SEX; error messages indicate that the
    SQL> -- constraint EMP_SEX_VALUES depends on the column SEX:
    SQL> --
    SQL> ALTER TABLE EMPLOYEES DROP COLUMN SEX;
    %RDB-E-NO_META_UPDATE, metadata update failed
    -RDMS-F-FLDINCON, field SEX is referenced in constraint EMP_SEX_VALUES
    -RDMS-F-RELFLDNOD, field SEX has not been deleted
    from relation EMPLOYEES
    SQL> --
    SQL> -- Delete the constraint EMP_SEX_VALUES:
    SQL> --
    SQL> ALTER TABLE EMPLOYEES DROP CONSTRAINT EMP_SEX_VALUES;
    SQL> --
    SQL> -- Because EMP_SEX_VALUES was the only constraint or index
    SQL> -- that depended on the column SEX, you can now delete
    SQL> -- the column SEX:
    SQL> --
    SQL> ALTER TABLE EMPLOYEES DROP COLUMN SEX;
    SQL> --
    SQL> -- The column SEX in the table EMPLOYEES was the only column in
    SQL> -- the database that depended on the domain SEX_DOM, so you can
    SQL> -- now delete the domain SEX_DOM:
    SQL> --
    SQL> DROP DOMAIN SEX_DOM;
    SQL>