ORACLE 关连更新 update select

 

总结:  关键的地方是where 语句的加入. 在11G中, 如果不加11G , 或造成除匹配的行数更新为相应的值之后, 其余的会变成负数. 

    所以, 测试的办法就是:  先查看需要更新的数量即连接的数量究竟有多少行, 然后update 之后多少行, 才能确定条件是否正确.

 

引入知识比较全面的地址: 

 

 

本人用到的2处SQL:

1 :   

  1. UPDATE SFISM4.R_DT_DIP_TRACEABILITY_T B
  2. SET (B.CURRENT_QTY, B.UPDATE_TIME, B.UPDATE_USER)=
  3. (SELECT DECODE(SIGN(B.CURRENT_QTY - A.KP_COUNT),
  4. -1,
  5. 0,
  6. B.CURRENT_QTY - A.KP_COUNT),
  7. SYSDATE,
  8. :VUSER
  9. FROM SFIS1.C_DT_DIP_BOM_T A, SFISM4.R_MO_BASE_T C
  10. WHERE A.BOM_NO = B.BOM_NO
  11. AND B.BOM_NO = C.KEY_PART_NO
  12. AND A.KEY_PART_NO = B.KEY_PART_NO
  13. AND C.MO_NUMBER =:VBOM
  14. AND B.TRAC_LOT =:VTRACELOT)
  15. WHERE B.TRAC_LOT =:VTRACELOT
  16. AND EXISTS (SELECT 1
  17. FROM SFIS1.C_DT_DIP_BOM_T AA
  18. WHERE B.BOM_NO = AA.BOM_NO
  19. AND B.KEY_PART_NO = AA.KEY_PART_NO)
  20. UPDATE SFISM4.R_REEL_TRACKING_T A
  21. SET A.REMAIN_QTY =
  22. (SELECT B.REEL_QTY
  23. FROM SFISM4.R_MMS_STOCK_SMT_SA_DETAIL_T B
  24. WHERE A.REEL_ID = B.REEL_ID
  25. AND A.REMAIN_QTY <0
  26. AND A.REMAIN_QTY <> B.REEL_QTY)
  27. WHERE EXISTS (SELECT 1
  28. FROM SFISM4.R_MMS_STOCK_SMT_SA_DETAIL_T B
  29. WHERE A.REEL_ID = B.REEL_ID
  30. AND A.REMAIN_QTY <0
  31. AND A.REMAIN_QTY <> B.REEL_QTY);
 
2: 
  1. UPDATE SFISM4.R_REEL_TRACKING_T A
  2. SET A.REMAIN_QTY =
  3. (SELECT B.REEL_QTY
  4. FROM SFISM4.R_MMS_STOCK_SMT_SA_DETAIL_T B
  5. WHERE A.REEL_ID = B.REEL_ID
  6. AND A.REMAIN_QTY <0
  7. AND A.REMAIN_QTY <> B.REEL_QTY)
  8. WHERE EXISTS (SELECT 1
  9. FROM SFISM4.R_MMS_STOCK_SMT_SA_DETAIL_T B
  10. WHERE A.REEL_ID = B.REEL_ID
  11. AND A.REMAIN_QTY <0
  12. AND A.REMAIN_QTY <> B.REEL_QTY);
 
最后是引用比较好的说明如下, 进行标注: 原文网址: http://www.blogjava.net/Jhonney/archive/2010/06/25/324503.html
 

SQL> select * from wwm2;        --要更新的表 , 多一点. 

TOWN                         ID
-------------------- ----------
222                         222
111                         111
ww‘jj                       111
llll                       1111
dddd                       2222
lllldf                      111
lllldf                      111
dsafdf                      111
3435                        111
ljjjjj                      222
dsafdf                      111
TOWN                         ID
-------------------- ----------
3435                        111
ljjjjj                      222

SQL> select * from wwm5;            --更新的条件表 , 少一点
TOWN                         ID
-------------------- ----------
lllldf                      111
test                       9984
SQL> select wwm2.* from wwm2,wwm5 where wwm2.id=wwm5.id
  2  /
TOWN                         ID
-------------------- ----------
111                         111
ww‘jj                       111
lllldf                      111
lllldf                      111
dsafdf                      111
3435                        111
dsafdf                      111
3435                        111
8 rows selected.
所以,每次需要更新8条数据就是正确的. 这一步是验证更新是不是对, 错的关键.!!!
相信程序员是通过以下类似的SQL更新的,这是错误的,因为没有加WHERE
SQL>  update wwm2 set wwm2.town=(select wwm5.town from wwm5 where wwm5.id=wwm2.id)
  2  /
13 rows updated.
SQL> select * from wwm2;
TOWN                         ID
-------------------- ----------
                            222
lllldf                      111
lllldf                      111
                           1111
                           2222
lllldf                      111
lllldf                      111
lllldf                      111
lllldf                      111
                            222
lllldf                      111
TOWN                         ID
-------------------- ----------
lllldf                      111
                            222
13 rows selected.
可以看到13条记录被更新,符合条件的更新正确,不符合条件的也更新为NULL.以下是正确的方法
方法一:
SQL> update wwm2
  2  set town=(select town from wwm5 where wwm5.id=wwm2.id)
  3  where id=(select wwm5.id from wwm5 where wwm5.id=wwm2.id)
  4  /
8 rows updated.
方法二:    与方法一道理相同,这里需要掌握EXIST的相关用法.
SQL> update wwm2
   set town=(select town from wwm5 where wwm5.id=wwm2.id)
   where exists (select 1 from wwm5 where wwm5.id=wwm2.id)
8 rows updated.
方法三:
SQL> update (select a.town atown,a.id aid,b.town btown,b.id bid from wwm2 a,wwm5 b where a.id=b.id)
  2  set atown=btown
  3  /
set atown=btown
    *
ERROR at line 2:
ORA-01779: cannot modify a column which maps to a non key-preserved table
  1* alter table wwm5 add primary key (id)
SQL> /
Table altered.
  1  update (select a.town atown,a.id aid,b.town btown,b.id bid from wwm2 a,wwm5 b where a.id=b.id) -- 表连接之后, 更新视图的方式很好理解. 但是需要primary key.
  2*  set atown=btown
SQL> /
8 rows updated.
这种方法的局限性就是需要PRIMARY 的支持.! 需要 更新被更新表有主键, 连接栏位是不是需要呢>? 
方法四: --万金油. 但是数据库顾问说效能没有使用表连接好.
  1  declare
  2  cursor cur_wwm is select town,id from wwm5; -- 驱动 表
  3  begin
  4     for my_wwm in cur_wwm loop
  5     update wwm2 set town=my_wwm.town -- 被驱动表.
  6     where id=my_wwm.id;
  7     end loop;
  8* end;
SQL> /
PL/SQL procedure successfully completed.
SQL> select * from wwm2;
TOWN                         ID
-------------------- ----------
222                         222
lllldf                      111
lllldf                      111
llll                       1111
dddd                       2222
lllldf                      111
lllldf                      111
lllldf                      111
lllldf                      111
ljjjjj                      222
lllldf                      111
TOWN                         ID
-------------------- ----------
lllldf                      111
ljjjjj                      222
这个方法是最灵活的了.
方法五:
注意,方法五只能适用于WWM5是WWM2的子集的时候. (新特性 merge Into,哎呀! 不想学.....)
  1   merge into wwm2
  2   using (select town,id from wwm5) b
  3   on (wwm2.id=b.id)
  4   when matched then update set town=b.town
  5* when not matched then insert (town,id) values (null,null)
SQL> /
9 rows merged.
SQL> select * from wwm2;
TOWN                         ID
-------------------- ----------
                                  ---注意这个地方,被插入了一个空值.因为WWM5的ID=9984在WWM2中不能匹配,根本原因是ORACLE9必须有WHEN NOT MATCHED子句,但是ORACLE10可以不许要,也就是ORACLE10可以不写WHEN NOT MATCHED ,就不必插入NULL值了,为解决这个问题,下一步会DELETE WWM5的ID=9984,这样一来就不会执行WHEN NOT MATCHED
222                         222
lllldf                      111
lllldf                      111
llll                       1111
dddd                       2222
lllldf                      111
lllldf                      111
lllldf                      111
lllldf                      111
ljjjjj                      222
TOWN                         ID
-------------------- ----------
lllldf                      111
lllldf                      111
ljjjjj                      222
14 rows selected.
SQL> delete from wwm5 where id=9984;
1 row deleted.
SQL>  1   merge into wwm2                             
SQL>   2   using (select town,id from wwm5) b
SQL>   3   on (wwm2.id=b.id)
SQL>   4   when matched then update set town=b.town
SQL>   5* when not matched then insert (town,id) values (null,null)
SQL> /
8 rows merged.
 
       以上就是5种关连更新的例子了,希望能给开发人员解惑.
 
说明:如果select 子句可以返回多行记录,但返回适合where条件的记录只能是唯一的,否则将会报返回单行的select子句返回多行的错误,因为update只能跟据此处的where子句(内层where)进行相应记录的匹配更新,一次只能是一条。
    





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