我有一个表表示与另一个表中的单个行相关的一组值.我可以通过删除所有值并添加新集合,或者通过有选择地删除某些值并添加其他值来更改这些值,但是如果可能,我有兴趣将其设置为单个语句.
这是一个更新的工作示例.为了使这项工作,我不得不添加虚拟,以便一列可用于更新,不是在条件.有没有办法只删除和插入没有一个虚拟列来更新？
即使没有实际更新,也不能在更新设置列表中显示条件的列.
create table every_value ( the_value varchar2(32) );
create table paired_value ( the_id number,a_value varchar2(32),dummy number default 0 );
-- the_id is a foreign_key to a row in another table
insert into every_value ( the_value ) values ( 'aaa' );
insert into every_value ( the_value ) values ( 'abc' );
insert into every_value ( the_value ) values ( 'ace' );
insert into every_value ( the_value ) values ( 'adg' );
insert into every_value ( the_value ) values ( 'aei' );
insert into every_value ( the_value ) values ( 'afk' );
-- pair ace and afk with id 3
merge into paired_value p using every_value e
on ( p.the_id = 3 and p.a_value = e.the_value )
when matched then update set dummy=dummy+1
delete where a_value not in ('ace','afk')
when not matched then insert (the_id,a_value)
values (3,e.the_value)
where e.the_value in ('ace','afk');
-- pair ace and aei with id 3
-- should remove afk,add aei,do nothing with ace
merge into paired_value p using every_value e
on ( p.the_id = 3 and p.a_value = e.the_value )
when matched then update set dummy = dummy+1
delete where a_value not in ('ace','aei')
when not matched then insert (the_id,'aei');
-- pair aaa and adg with id 4
merge into paired_value p using every_value e
on ( p.the_id = 4 and p.a_value = e.the_value )
when matched then update set dummy = dummy+1
delete where a_value not in ('aaa','adg')
when not matched then insert (the_id,a_value)
values (4,e.the_value)
where e.the_value in ('aaa','adg');
select * from paired_value;
我已经在oracle 10g中试过了,而这个sqlfiddle,oracle 11g.
这里是文档： http://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_9016.htm
Specify the DELETE where_clause to clean up data in a table while
populating or updating it. The only rows affected by this clause are
those rows in the destination table that are updated by the merge
operation. The DELETE WHERE condition evaluates the updated value,not
the original value that was evaluated by the UPDATE SET … WHERE
condition. If a row of the destination table meets the DELETE
condition but is not included in the join defined by the ON clause,
then it is not deleted. Any delete triggers defined on the target
table will be activated for each row deletion.
这意味着必须更新行. Hovewer,您不需要更新所有行,UPDATE后使用与DELETE中使用的相同的WHERE子句
when matched then update set dummy=dummy
where a_value not in ('ace','afk')
delete
where a_value not in ('ace','afk')
