Sir, I am using these codes with sqlserver 2008.

I am trying to get data from two tables like this

SELECT Date, DatePart(hour,Date) as Hr, reading
FROM TABLE1 A
WHERE Date = 

(SELECT Min(Date) as date
 FROM TABLE1 B
 WHERE DatePart(hour,A.Date)= DatePart(hour,B.Date) 

 union all

 SELECT Min(Date)as date
 FROM TABLE2 C
 WHERE DatePart(hour,A.Date)= DatePart(hour,C.Date)) 

but I am facing this error message


Msg 512, Level 16, State 1, Line 1
Subquery returned more than 1 value. This is not permitted when the subquery follows or when the subquery is used as an expression.

How to overcome this?


But this query work fine

SELECT Date, DatePart(hour,Date) as Hr, reading
FROM TABLE1 A
WHERE Date = 

(SELECT Min(Date) as date
 FROM TABLE1 B
 WHERE DatePart(hour,A.Date)= DatePart(hour,B.Date) ) 

Please