oracle外键约束语句【关于oracle外键引用与goldengate】

一、准备知识

约束放置在表中，有以下五种约束:

NOT NULL 非空约束C 指定的列不允许为空值

UNIQUE 唯一约束U 指定的列中没有重复值，或该表中每一个值或者每一组值都将是唯一的

PRIMARY KEY 主键约束P 唯一的标识出表的每一行,且不允许空值值,一个表只能有一个主键约束

FOREIGN KEY 外键约束R 一个表中的列引用了其它表中的列，使得存在依赖关系，可以指向引用自身的列

CHECK 条件约束C 指定该列是否满足某个条件

约束命名规则

如果不指定约束名Oracle server 自动按照SYS_Cn 的格式指定约束名，也可手动指定，

推荐的约束命名是：约束类型_表名_列名。

NN：NOT NULL 非空约束，比如nn_emp_sal

UK：UNIQUE KEY 唯一约束

PK：PRIMARY KEY 主键约束

FK：FOREIGN KEY 外键约束

CK：CHECK 条件约束

外键约束是用来维护从表和主表的引用完整性的，所以外键约束要涉及两个表。

FOREIGN KEY: 在表级指定子表中的列

REFERENCES: 标示在父表中的列

ON DELETE CASCADE: 当父表中的列被删除时，子表中相对应的列也被删除

ON DELETE SET NULL: 子表中相应的列置空

二、外键创建测试

foreign_main为主表

foreign_sub为从表

object_id做为foreign_sub的外键，参考主表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.

建议使用主表的主键做外键，即使不是主表的主键也应该是唯一约束的字段做为外键

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.

从表插入一条主表object_id中不存在的记录测试

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

提示主表数据不存在，从表不能创建主表不存在的object_id以保证完整性

三、级联删除测试

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下仍然不能单独更新主表外键字段

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模式下可以通过主表删除外键字段数据关联删除从表数据

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

外键相关常用操作及参考文档

建立外键

alter table 表名 add constraint 外键名 foreign key(从表外键字段) references foreign_main(主表外键字段);

drop表外键

alter table 表名 drop constraint 外键名;

通过外键找表

select * from user_constraints where constraint_type="R" and constraint_name=upper("外键名");

通过表找外键

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

查找表的外键(包括名称，引用表的表名和对应的键名，下面是分成多步查询)：

select * from user_constraints c where c.constraint_type = "R" and c.table_name = 要查询的表

查询引用表的键的列名：

select * from user_cons_columns cl where cl.constraint_name = 外键引用表的键名

外键约束临时disabled

alter table 表名 disable constraint 外键名;

在SQL92标准中定义了几种外键改变后，如何处理子表记录的动作，其中包括：

限制Restrict：这种方式不允许对被参考的记录的键值执行更新或删除的操作;置为空Set to null：当参考的数据被更新或者删除，那么所有参考它的外键值被置为空;

置为默认值Set to default：当参考的数据被更新或者删除，那么所有参考它的外键值被置为一个默认值;

级联Cascade：当参考的数据被更新，则参考它的值同样被更新，当参考的数据被删除，则参考它的子表记录也被删除;

不做操作No action：这种方式不允许更新或删除被参考的数据。和限制方式的区别在于，这种方式的检查发生在语句执行之后。Oracle默认才会的方式就是这种方式。

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 没有禁用外键约束会出现以现错误

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

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 = 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 ERROR OGG-01296 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Error mapping from SCOTT.FOREIGN_MAIN to SCOTT.FOREIGN_MAIN.

2013-12-26 04:51:25 WARNING OGG-01525 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Failed to open trace output file, "gglog-REP_APP.dmp", error 13 (Permission denied).

2013-12-26 04:51:25 ERROR OGG-01668 Oracle GoldenGate Delivery for Oracle, rep_app.prm: PROCESS ABENDING.

2013-12-26 04:52:20 INFO OGG-00996 Oracle GoldenGate Delivery for Oracle, rep_app.prm: REPLICAT REP_APP started.

2013-12-26 04:52:20 WARNING OGG-00869 Oracle GoldenGate Delivery for Oracle, rep_app.prm: No unique key is defined for table "FOREIGN_SUB". All viable columns will be used to represent the key, but may not guarantee uniqueness. KEYCOLS may be used to define the key.

2013-12-26 04:52:20 WARNING OGG-01004 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Aborted grouped transaction on "SCOTT.FOREIGN_SUB", Database error 1403 (OCI Error ORA-01403: no data found, SQL ).

2013-12-26 04:52:20 WARNING OGG-01003 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Repositioning to rba 17426 in seqno 29.

2013-12-26 04:52:20 WARNING OGG-01154 Oracle GoldenGate Delivery for Oracle, rep_app.prm: SQL error 1403 mapping SCOTT.FOREIGN_SUB to SCOTT.FOREIGN_SUB OCI Error ORA-01403: no data found, SQL .

2013-12-26 04:52:20 WARNING OGG-01003 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Repositioning to rba 17426 in seqno 29.

2013-12-26 04:52:20 ERROR OGG-01296 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Error mapping from SCOTT.FOREIGN_SUB to SCOTT.FOREIGN_SUB.

2013-12-26 04:52:20 WARNING OGG-01525 Oracle GoldenGate Delivery for Oracle, rep_app.prm: Failed to open trace output file, "gglog-REP_APP.dmp", error 13 (Permission denied).

2013-12-26 04:52:20 ERROR OGG-01668 Oracle GoldenGate Delivery for Oracle, rep_app.prm: PROCESS ABENDING.