ORACLE 关连更新 update select

日月明王 http://sunmoonking.spaces.live.com 今天写了个复杂的SQL,用来更新另一个表 select vin,(max(in_mileage)-min(in_mileage))/(max(start_time)-min(start_time)) from (select vin,in_mileage,start_timefrom (select vin,in_mileage,start_time ,r

日月明王

http://sunmoonking.spaces.live.com

今天写了个复杂的SQL,用来更新另一个表

select vin,(max(in_mileage)-min(in_mileage))/(max(start_time)-min(start_time)) from (  select vin,in_mileage,start_time  from (select vin,in_mileage,start_time ,  row_number() over (partition by vin order by start_time) wwmnum from (select  vin,max(in_mileage) in_mileage,max(start_time) start_time from (select vin,in_mileage,start_time from tt_repair_order   union select vin,in_mileage,start_time  from tt_ro_balanced)   group by vin,to_char(start_time,'yyyymmdd') ) )  where wwmnum0 and to_char(max(start_time),'yyyymmdd')to_char(min(start_time),'yyyymmdd')

写完这个SQL交给程序员后,程序员跟我说不会UPDATE,也就是说通过B表更新A表程序员是有困难的,于是在这里整理下各种不同的方法以供以后使用.

$ sqlplus user/pass

SQL*Plus: Release 9.2.0.6.0 - Production on Wed Aug 2 17:38:39 2006

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

Connected to: Oracle9i Enterprise Edition Release 9.2.0.6.0 - 64bit Production With the Partitioning, OLAP and Oracle Data Mining options JServer Release 9.2.0.6.0 - Production

SQL> select * from wwm2;        --要更新的表

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

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.

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)   2*  set atown=btown SQL> /

8 rows updated.

这种方法的局限性就是需要PRIMARY 的支持.

方法四:   1  declare   2  cursor cur_wwm is select town,id from wwm5;   3  begin   4     for my_wwm in cur_wwm loop   5     update wwm2 set town=my_wwm.town   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.   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.