constraints,테이블 변경

Syntax:

   ALTER TABLE [schema.]table

      constraint_clause [,…]

          [ENABLE enable_clause | DISABLE disable_clause]

              [{ENABLE|DISABLE} TABLE LOCK]

                 [{ENABLE|DISABLE} ALL TRIGGERS];

constraint_clause:

   ADD out_of_line_constraint(s)

   ADD out_of_line_referential_constraint

   DROP PRIMARY KEY [CASCADE] [{KEEP|DROP} INDEX]

   DROP UNIQUE (column [,…]) [{KEEP|DROP} INDEX]

   DROP CONSTRAINT constraint [CASCADE]

   MODIFY CONSTRAINT constraint constrnt_state

   MODIFY PRIMARY KEY constrnt_state

   MODIFY UNIQUE (column [,…]) constrnt_state

   RENAME CONSTRAINT constraint TO new_name

constrnt_state:   

    [[NOT] DEFERRABLE] [INITIALLY {IMMEDIATE|DEFERRED}]

       [RELY | NORELY] [USING INDEX using_index_clause]

          [ENABLE|DISABLE] [VALIDATE|NOVALIDATE]

              [EXCEPTIONS INTO [schema.]table]

Examples

Add a column to a table:

   ALTER TABLE STAFF_OPTIONS

      ADD SO_INSURANCE_PROVIDER Varchar2(35);

Add a default value to a column:

   ALTER TABLE STAFF_OPTIONS

      MODIFY SO_INSURANCE_PROVIDER Varchar2(35) DEFAULT 'ABC Ins';

Add two columns to a table and remove a constraint:

   ALTER TABLE STAFF_OPTIONS

      ADD (SO_STAFF_ID INT, SO_PENSION_ID INT)

          STORAGE INITIAL 10 K

          NEXT 10 K

          MAXEXTENTS 121

          PCTINCREASE 0

          FREELISTS 2

      DROP CONSTRAINT cons_SO;

PK와 FK는 변경이 불가능..

출처 :  http://ss64.com/ora/table_a_cons.html