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oracle更新多表BYPASS_UJVC

oracle 多表连合修改—-BYPASS_UJVC
方法一:
ORA-01779: cannot modify a column which maps to a non-key-preserved table
例如,使用以下的更新查询就会出现该错误。
CREATE TABLE test1 ( id integer primary key, num integer );
INSERT INTO test1 VALUES (1,0);
INSERT INTO test1 VALUES (2,0);
INSERT INTO test1 VALUES (3,0);
INSERT INTO test1 VALUES (4,0);
CREATE TABLE test2 ( id integer, num integer, upd integer );
INSERT INTO test2 VALUES (1,10, 0);
INSERT INTO test2 VALUES (2,20, 1);
UPDATE ( SELECT t1.id id1, t1.num num1, t2.id id2, t2.num num2
FROM test1 t1, test2 t2 WHERE t1.id=t2.id AND t2.upd=1 )
SET num1=num2; ORA-01779: cannot modify a column which maps to a non-key-preserved table
这个错误的意思是,子查询的结果中,更新数据源(test2)的内容不唯一,导致被更新对象(test1)中的一行可能对应数据源(test2)中的多行。 本例中,test2表的id不唯一,因此test2表中可能存在id相同但是num不相同的数据,这种数据是无法用来更新 test1 的。

解决方法就是保证数据源的唯一性,例如本例中可以为test2.id创建一个唯一索引:

CREATE UNIQUE INDEX test2_idx_001 ON test2 (id);
之后上面的更新就可以执行了。

另外也可以强制 Oracle 执行,方法是加上 BYPASS_UJVC 注释。

UPDATE
( SELECT /*+ BYPASS_UJVC */ t1.id id1, t1.num num1, t2.id id2, t2.num num2
FROM test1 t1, test2 t2
WHERE t1.id=t2.id AND t2.upd=1 )
SET num1=num2;
BYPASS_UJVC的作用是跳过Oracle的键检查。 这样虽然能够执行了,但是如果test2中存在不唯一的数据,test1就会被更新多次而导致意想不到的结果。

方法二:
update (select /*+ BYPASS_UJVC */ name , rname
from table1 t1, table2 t2
where t1.id = t2.id
and t1.id is not null)
set name = rname

— 对应的MERGE格式()
— 只更新不插入的语法 只有10g才能支持,9i还不能支持!
— 因此如果是9i,则还是要使用对视图的UPDATE语句
MERGE INTO david_1 T1
USING david_2 T2
ON (T1.A = T2.A AND t1.a <=2)
WHEN MATCHED THEN
UPDATE
SET T1.B = T2.B
–WHEN NOT MATCHED THEN NOTHING

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  1. Verda Faughnan | #1
    2011-12-21 at 04:59

    Howdy this is somewhat of off topic but I was wondering if blogs use WYSIWYG editors or if you have to manually code with HTML. I’m starting a blog soon but have no coding skills so I wanted to get guidance from someone with experience. Any help would be enormously appreciated!

  2. Marylada | #2
    2011-06-16 at 19:05

    Home run! Great slgnugig with that answer!

    • Celina | #3
      2011-06-22 at 17:26

      Thanks guys, I just about lost it loknoig for this.