Question

我在SQL中有3个表用户
UserID|UserName|password
1:John:abc123
2:Sara:asdfr
AppRights
apprightkey|description
removedata:Can Remove Data
adddata:Can Insert New Data
viewdata:Only Can View Data
UserRights
userid|rightkey
1:adddata
1:removedata
2:removedata

以下是我想通过插入用户ID来获取AppRights表中的描述的问题，但只有UserRights表中可用的那些。
我也尝试了这样但结果没有返回任何内容 select Decsription from AppRights where AppRigthKey = (select RrightKey from UserRights where userid=1);

Answer 1

试试这个，

select Decsription 
from AppRights 
where AppRigthKey = (select RrightKey from UserRights);

我认为，你的查询中有一些拼写错误。试试我的回答：

DECLARE @Users TABLE(UserID INT, UserName VARCHAR(10),password VARCHAR(10))
INSERT INTO @Users VALUES(1,'John','abc123')
INSERT INTO @Users VALUES(2,'Sara','asdfr')

DECLARE @AppRights TABLE(apprightkey VARCHAR(100),description VARCHAR(100))
INSERT INTO @AppRights VALUES('removedata','Can Remove Data')
INSERT INTO @AppRights VALUES('adddata','Can Insert New Data')
INSERT INTO @AppRights VALUES('viewdata','Only Can View Data')

DECLARE @UserRights TABLE(userid INT,rightkey VARCHAR(100))
INSERT INTO @UserRights VALUES(1,'adddata')
INSERT INTO @UserRights VALUES(1,'removedata')
INSERT INTO @UserRights VALUES(2,'removedata')

select description 
from @AppRights 
where apprightkey IN (select rightkey from @UserRights where userid=1);

请尝试以下表格：

select description 
from AppRights 
where apprightkey IN (select rightkey from UserRights where userid=1);

Answer 2

这是有效的语法：

select Decsription from AppRights 
where AppRigthKey = (select RrightKey from UserRights);

但是您确实需要确保子查询只返回一个值，这是确保这一点的一种方法：

select Decsription from AppRights 
where AppRigthKey = (select max(RrightKey) from UserRights);

或者，使用IN可能会有所帮助，因为这允许子查询返回多个值。

select Decsription from AppRights 
where AppRigthKey IN (select RrightKey from UserRights);

然而，这也可能使查询显示更多行。

Answer 3

请注意，您的子查询应返回一行

SELECT field1 from TABLE1 where field1 = (SELECT field2 from TABLE2)

或者如果它返回更多那个你可以使用IN语句

SELECT field1 from TABLE1 where field1 IN (SELECT field2 from TABLE2)

在你的情况下可能就像

select Decsription from AppRights where AppRigthKey IN (select RrightKey from UserRights);

从条件三个表中获取数据

3 个答案: