Question

两个表：

StoreInfo:
UserId uniqueidentifier
StoreNo nvarchar
UserName nvarchar
Password nvarchar

UserInfo:
UserId uniqueidentifier
UserName nvarchar
Password nvarchar

StoreInfo上的UserId当前为空。如何使用UserInfo的UserId基于StoreInfo的UserName更新StoreInfo的UserId，并且Password与UserInfo中的UserName和Password匹配。

以下是我编写的查询，它使用UserInfo中的第一个UserId更新StoreInfo中的整个UserId，所以我知道这是错误的。

declare @UserName nvarchar(255)
declare @Password nvarchar(25)
declare @UserId uniqueidentifier

select @UserName = UserName, @Password = Password, @UserId = UserId
from UserInfo

select UserId, Password 
   from FranchiseInfo 
   where UserID = @UserName and Password = @Password

update FranchiseInfo
set UserI = @UserId

Answer 1

更新看起来像这样

update storeinfo
set userid = u.userid
from userinfo u 
inner join storeinfo s on (s.username = u.username and s.password = u.password)
where userid is null

Answer 2

UPDATE StoreInfo
 set UserId = ui.UserId
 from StoreInfo si
  inner join UserInfo ui
   on ui.UserName = si.UserName
    and ui.Password = si.Password
 where si.UserId is null

这将更新表中未设置UserId的所有行。如果您只想更新选定的行，请构建where子句。（我没有测试过，所以请注意拼写错误！）

Answer 3

最有效的方法是UPDATE ... FROM语法，例如

UPDATE StoreInfo
SET
    UserId = ui.UserId
FROM
    StoreInfo si
    INNER JOIN UserInfo ui ON ui.UserName = si.UserName AND ui.Password = si.Password;

如何根据条件更新表列？

3 个答案: