sql-halemp表
Excel表
导入Excel表后进行更新
发现sql表中存在的，excel表中没有的记录会改变为空值，如何加判断，谢谢
update Halemp set
sbjs = (select sbjs from excel b where Halemp.ecode = b.ecode),
gjjjs = (select gjjjs from excel b where Halemp.ecode = b.ecode)
------解决思路----------------------
加exists条件啊
update Halemp a
set sbjs = (select sbjs from excel b where a.ecode = b.ecode),
gjjjs = (select gjjjs from excel b where a.ecode = b.ecode)
where exists (selct 1 from excel c where a.ecode = c.ecode )