Question

what I need to test for on my table is if there are rows for a given user id and order id on two separate days (DATETIME field for a timestamp).

I’m pretty sure I’d need a having clause and that’s why I’m here…that frightens me terribly.

Answer 1

Having shouldn’t scare you, it is just a “Where” on an aggregated field:

Select UserID, Count(*) From OrderTbl Group By UserID Having Count(*) > 1

That’ll give you all the Users that have multiple orders.

Select UserID, Count(*) From OrderTbl Where (UserID=@UserID) Group By UserID Having Count(*) > 1 

will give you the count if there are multiple records for the user id in @UserID and null if not.

if exists (Select UserID, Count(*) From OrderTbl Where (UserID=@UserID) Group By UserID 
             Having Count(*) > 1) Select 1 else Select 0

will return a 1 if there are multiple records for the User, 0 if not.

Update: Didn’t realize that you could have multiple orders per day. This query will do what you want:

With DistinctDates as (Select Distinct UserID, [DATE] From OrderTbl Where (UserID=@UserID))
Select UserID, Count(*) From DistinctDates  
Group By UserID Having Count(*) > 1