SQL進階一：ISERT INTO (<select clause> WITH CHECK OPTION) values (...)

insert into (<select clause> WITH CHECK OPTION) values (...)

例如：

SQL> insert into (select object_id,object_name,object_type from xxx where object_id<1000  WITH CHECK OPTION)
 2  values(999,'testbyhao','testtype');

這樣的語法看起來很特殊，其實是insert進subquery裏的這張表裏，只不過如果不滿足subquery裏的where條件的話，就不允許插入。

如果插入的列有不在subquery作爲檢查的where條件裏，那麼也會不允許插入。

如果不加WITH CHECK OPTION則在插入時不會檢查。

這裏注意，subquery其實是不會實際執行的。

例如：

SQL> insert into (select object_id,object_name,object_type from xxx where object_id<1000)
 2  values(1001,'testbyhao','testtype');

1 row created.

SQL> insert into (select object_id,object_name,object_type from xxx where object_id<1000with check option)
 2  values(1001,'testbyhao','testtype');
insert into (select object_id,object_name,object_type from xxx where object_id<1000 with check option)
                                                          *
ERROR at line 1:
ORA-01402: view WITH CHECK OPTION where-clause violation

這裏插入的列中沒有object_id，也是不允許插入的：

SQL> insert into (select object_name,object_type from xxx where object_id<1000 with check option)
 2  values('testbyhao','testtype');
insert into (select object_name,object_type from xxx where object_id<1000 with check option)
                                                *
ERROR at line 1:
ORA-01402: view WITH CHECK OPTION where-clause violation

爲什麼說subquery沒有實際執行呢？看統計信息吧：

SQL> set autotrace trace exp stat
SQL> select object_id,object_name,object_type from xxx where object_id<1000;

955 rows selected.

       197  consistent gets

SQL> insert into (select object_id,object_name,object_type from xxx where object_id<1000)
 2  values(999,'testbyhao','testtype');

1 row created.

         1  consistent gets