關於oracle外鍵引用與goldengate

 　　一、准備知識

　　約束放置在表中，有以下五種約束:

　　NOT NULL 非空約束C 指定的列不允許為空值

　　UNIQUE 唯一約束U 指定的列中沒有重復值，或該表中每一個值或者每一組值都將是唯一的

　　PRIMARY KEY 主鍵約束P 唯一的標識出表的每一行,且不允許空值值,一個表只能有一個主鍵約束

　　FOREIGN KEY 外鍵約束R 一個表中的列引用了其它表中的列，使得存在依賴關系，可以指向引用自身的列

　　CHECK 條件約束C 指定該列是否滿足某個條件

　　約束命名規則

　　如果不指定約束名Oracle server 自動按照SYS_Cn 的格式指定約束名，也可手動指定，

　　推薦的約束命名是：約束類型_表名_列名。

　　NN：NOT NULL 非空約束，比如nn_emp_sal

　　UK：UNIQUE KEY 唯一約束

　　PK：PRIMARY KEY 主鍵約束

　　FK：FOREIGN KEY 外鍵約束

　　CK：CHECK 條件約束

　　外鍵約束是用來維護從表和主表的引用完整性的，所以外鍵約束要涉及兩個表。

　　FOREIGN KEY: 在表級指定子表中的列

　　REFERENCES: 標示在父表中的列

　　ON DELETE CASCADE: 當父表中的列被刪除時，子表中相對應的列也被刪除

　　ON DELETE SET NULL: 子表中相應的列置空

　　二、外鍵創建測試

　　foreign_main為主表

　　foreign_sub為從表

　　object_id做為foreign_sub的外鍵，參考主表foreign_main的object_id值

　　SQL> create table foreign_main as select object_id from all_objects;

　　Table created.

　　SQL> select count(*) from foreign_main;

　　COUNT(*)

　　----------

　　49571

　　SQL> create table foreign_sub as select object_id,object_name from all_objects;

　　Table created.

　　建議使用主表的主鍵做外鍵，即使不是主表的主鍵也應該是唯一約束的字段做為外鍵

　　SQL> alter table foreign_main add constraint pk_fsid primary key(object_id);

　　Table altered.

　　SQL> delete from foreign_sub where object_name = 'FOREIGN_MAIN';

　　1 row deleted.

　　SQL> commit;

　　Commit complete.

　　SQL> alter table foreign_sub add constraint fr_fssid foreign key(object_id) references foreign_main(object_id);

　　Table altered.

　　從表插入一條主表object_id中不存在的記錄測試

　　SQL> insert into foreign_sub values(1,'ts');

　　insert into foreign_sub values(1,'ts')

　　*

　　ERROR at line 1:

　　ORA-02291: integrity constraint (TEST.FR_FSSID) violated - parent key not found

　　提示主表數據不存在，從表不能創建主表不存在的object_id以保證完整性

　　三、級聯刪除測試

　　SQL> alter table foreign_sub drop constraint fk_fs_oid;

　　Table altered.

　　SQL> alter table foreign_sub add constraint fk_fs_oid foreign key(object_id) references foreign_main(object_id) on delete cascade;

　　Table altered.

　　cascade下仍然不能單獨更新主表外鍵字段

　　SQL> update foreign_main set object_id=52012 where object_id=52010;

　　update foreign_main set object_id=52012 where object_id=52010

　　*

　　ERROR at line 1:

　　ORA-02292: integrity constraint (TEST.FK_FS_OID) violated - child record found

　　cascade模式下可以通過主表刪除外鍵字段數據關聯刪除從表數據

　　SQL> select * from foreign_sub where object_id=52010;

　　OBJECT_ID OBJECT_NAME

　　---------- ------------------------------

　　52010 IDX_BJNAME

　　SQL> delete from foreign_main where object_id=52010;

　　1 row deleted.

　　SQL> commit;

　　Commit complete.

　　SQL> select * from foreign_sub where object_id=52010;

　　no rows selected

　　外鍵相關常用操作及參考文檔

　　建立外鍵

　　alter table 表名 add constraint 外鍵名 foreign key(從表外鍵字段) references foreign_main(主表外鍵字段);

　　drop表外鍵

　　alter table 表名 drop constraint 外鍵名;

　　通過外鍵找表

　　select * from user_constraints where constraint_type='R' and constraint_name=upper('外鍵名');

　　通過表找外鍵

　　select * from user_constraints where constraint_type='R' and table_name=upper('表名');

　　查找表的外鍵(包括名稱，引用表的表名和對應的鍵名，下面是分成多步查詢)：

　　select * from user_constraints c where c.constraint_type = 'R' and c.table_name = 要查詢的表

　　查詢引用表的鍵的列名：

　　select * from user_cons_columns cl where cl.constraint_name = 外鍵引用表的鍵名

　　外鍵約束臨時disabled

　　alter table 表名 disable constraint 外鍵名;

　　在SQL92標准中定義了幾種外鍵改變後，如何處理子表記錄的動作，其中包括：

　　限制Restrict：這種方式不允許對被參考的記錄的鍵值執行更新或刪除的操作;置為空Set to null：當參考的數據被更新或者刪除，那麼所有參考它的外鍵值被置為空;

　　置為默認值Set to default：當參考的數據被更新或者刪除，那麼所有參考它的外鍵值被置為一個默認值;

　　級聯Cascade：當參考的數據被更新，則參考它的值同樣被更新，當參考的數據被刪除，則參考它的子表記錄也被刪除;

　　不做操作No action：這種方式不允許更新或刪除被參考的數據。和限制方式的區別在於，這種方式的檢查發生在語句執行之後。Oracle默認才會的方式就是這種方式。

　　Col OWNER FOR A6

　　COL R_OWNER FOR A6

　　COL TABLE_NAME FOR A15

　　select OWNER, TABLE_NAME, CONSTRAINT_NAME, CONSTRAINT_TYPE, R_OWNER, R_CONSTRAINT_NAME, DELETE_RULE from user_constraints where table_name in ('FOREIGN_MAIN', 'FOREIGN_SUB');

　　Select CONSTRAINT_NAME from user_constraints e where e.table_name='IMS_COLUMN' and owner='WSJD_ELMS6';

　　Select b.table_name,b.column_name, A.CONSTRAINT_TYPE, C.TABLE_NAME from user_constraints a, user_cons_columns b, user_constraints C

　　WHERE a.constraint_name = b.constraint_name AND

　　A.R_CONSTRAINT_NAME = C.CONSTRAINT_NAME

　　AND a.r_constraint_name IN (Select CONSTRAINT_NAME from user_constraints e where e.table_name='FOREIGN_MAIN' and owner='SCOTT');

　　create table foreign_sub as select object_id, object_name from user_objects;

　　create table foreign_main as select object_id from foreign_sub;

　　alter table foreign_main add constraint pk_foreign_main_object_id primary key(object_id);

　　alter table foreign_sub add constraint fr_foreign_sub_object_id foreign key(object_id) references foreign_main(object_id) on delete cascade;

　　alter table foreign_sub drop constraint fr_foreign_sub_object_id;

　　alter table foreign_sub disable constraint fr_foreign_sub_object_id;

　　如在goldengate 沒有禁用外鍵約束會出現以現錯誤

　　=============================================

　　2013-12-26 04:51:25 INFO OGG-00996 Oracle GoldenGate Delivery for Oracle, rep_app.prm: REPLICAT REP_APP started.

　　2013-12-26 04:51:25 WARNING OGG-00869 Oracle GoldenGate Delivery for Oracle, rep_app.prm: OCI Error ORA-02292: integrity constraint (SCOTT.FR_FOREIGN_SUB_OBJECT_ID) violated - child record found (status = 2292). DELETE FROM "SCOTT"."FOREIGN_MAIN" WHERE "OBJECT_ID" = :b0.

　　2013-12-26 04:51:25 WARNING OGG-01004 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Aborted grouped transaction on 'SCOTT.FOREIGN_MAIN', Database error 2292 (OCI Error ORA-02292: integrity constraint (SCOTT.FR_FOREIGN_SUB_OBJECT_ID) violated - child record found (status = 2292). DELETE FROM "SCOTT"."FOREIGN_MAIN" WHERE "OBJECT_ID" = :b0).

　　2013-12-26 04:51:25 WARNING OGG-01003 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Repositioning to rba 17426 in seqno 29.

　　2013-12-26 04:51:25 WARNING OGG-01154 Oracle GoldenGate Delivery for Oracle, rep_app.prm: SQL error 2292 mapping SCOTT.FOREIGN_MAIN to SCOTT.FOREIGN_MAIN OCI Error ORA-02292: integrity constraint (SCOTT.FR_FOREIGN_SUB_OBJECT_ID) violated - child record found (status =