update sfc_proutingdres set baseQTYN=a.v
from
(
select baseQTYN as v from sfc_operationres where operationid='1000000109'
) a
where sfc_proutingdres.PRoutingDId in (select sfc_proutingdres.PRoutingDId from sfc_proutingdres join sfc_proutingdetail on sfc_proutingdres.PRoutingDId=sfc_proutingdetail.PRoutingDId where operationid='1000000109')
这个SQL语句是什么意思？请大神指点，谢谢啦。
------解决思路----------------------
一条更新语句，
update sfc_proutingdres set baseQTYN=a.v --set 赋值语句 将后面查询中间结果看成表a,将a表中的字段v 赋值给sfc_proutingdres中的baseQTYN where语句描述的是将sfc_proutingdres.PRoutingDId满足什么条件的记录才执行更新
from
(
select baseQTYN as v from sfc_operationres where operationid='1000000109'
) a --表别名
where sfc_proutingdres.PRoutingDId in --更新条件
(select sfc_proutingdres.PRoutingDId from sfc_proutingdres join sfc_proutingdetail on sfc_proutingdres.PRoutingDId=sfc_proutingdetail.PRoutingDId where operationid='1000000109')--in（）是一个相同属性值的集合，由两张表通过join联结，联结字段是on后面的表达式，where进行删选符合条件的记录
------解决思路----------------------
; with t as (
select sfc_proutingdres.PRoutingDId
from sfc_proutingdres join sfc_proutingdetail
on sfc_proutingdres.PRoutingDId=sfc_proutingdetail.PRoutingDId
where operationid='1000000109') --- 要更新数据的条件之后
update sfc_proutingdres set baseQTYN=a.v
from (
select baseQTYN as v from sfc_operationres where operationid='1000000109' ) a -- 被更新数据要取 字段
where sfc_proutingdres.PRoutingDId in (select t.sfc_proutingdres from t
这个语句的主要用处是想要更新sfc_proutingdres 的baseQTYN这个字段，但是这个字段的取值是这个表中 operationid='1000000109' 的值，所以才会有临时表的数据，不过他没有关联这个里面的值，所以'1000000109' 对应值是多个的话， sfc_proutingdres 的baseQTYN这个字段值会是operationid='1000000109'的baseQTYN值。 条件是sfc_proutingdres.PRoutingDId在临时表中的数据，也就是你最后的那个where条件。