关于update的求教

[瘦小王]

如何通过一条update语句可以把图1的初始数据刷成图2这样的。也就是说把parent的value刷成child的value

[瘦小王]

引用 1 楼 baidu_36457652 的回复:

merge into t1
using (select id,parentid value from t1 where id<>parentid ) b
on( t1.id=b.parentid )
when matched then update set t1.value=b.value

好像mysql不支持merge into 的用法

[学海无涯-回头是岸]

引用 2 楼 king_bt 的回复:

好像mysql不支持merge into 的用法

那就直接用update吧 update t1 seet value=(select value from (select id,parentid value from t1 where id<>parentid ) b where t1.t1.id=b.parentid) where exists (select 1 from (select id,parentid value from t1 where id<>parentid ) b where t1.t1.id=b.parentid)

[瘦小王]

那就直接用update吧 update t1 seet value=(select value from (select id,parentid value from t1 where id<>parentid ) b where t1.t1.id=b.parentid) where exists (select 1 from (select id,parentid value from t1 where id<>parentid ) b where t1.t1.id=b.parentid)[/quote] 嗯，可以的，谢谢

[学海无涯-回头是岸]

merge into t1
using (select id,parentid value from t1 where id<>parentid ) b
on( t1.id=b.parentid )
when matched then update set t1.value=b.value