SQL Server - Subtracting results of two SQL Queries - sql

Question

I'm trying to results of two queries using Subquery in SQL Server.
What I'm trying to achieve is to Calculate number of customers that are part of "ProductX Promotion" and subtract the count of customers that are part of "ProductX Promotion" and have actually purchased ProductX within last 60 days. This gives me the count of enrolled customers who have not made ProductX purchase for better insights for marketing.
Initially I only had COUNT() hence it was easy to subtract the two. Now requirement is that the count broken down by State and Zip level of the customer. The problem arises here as I cannot use direct Subtraction, I tried NOT EXISTS but didn't work, I tried JOINs but still no luck. I know the solution is pretty simple but I cannot think of any.
Here's the original code with comments on what particular columns mean,
SELECT
(SELECT COUNT (DISTINCT (c.CustomerNumber))
FROM Customer c
INNER JOIN
TransactionDetail t
ON
c.CustomerNumber = t.CustomerNumber
WHERE c.ProductXPref = 1 --Indicates if Customer was part of ProductX promotion program.
AND t.TransactionDate > DATEADD(d, -60, getdate()))
-
(SELECT COUNT (DISTINCT c.CustomerNumber)
FROM Customer c
INNER JOIN
TransactionDetail t
ON
c.CustomerNumber = t.CustomerNumber
WHERE t.ProductXIndicator = 1 --Indicates if ProductX was purchased
AND t.TransactionDate > DATEADD(DD, -60, getdate())
AND c.ProductXPref = 1 --Indicates if Customer was part of ProductX promotion program.
) AS 'Column Name' INTO #TempTable1
Here's what I'm trying to implement,
SELECT
(SELECT c.Zip, c.State, COUNT (DISTINCT (c.CustomerNumber))
FROM Customer c
INNER JOIN
TransactionDetail t
ON
c.CustomerNumber = t.CustomerNumber
WHERE c.ProductXPref = 1
AND t.TransactionDate > DATEADD(d, -60, getdate())
GROUP BY c.Zip, c.State)
-
(SELECT c.Zip, c.State, COUNT (DISTINCT c.CustomerNumber)
FROM Customer c
INNER JOIN
TransactionDetail t
ON
c.CustomerNumber = t.CustomerNumber
WHERE t.ProductXIndicator = 1
AND t.TransactionDate > DATEADD(DD, -60, getdate())
AND c.ProductXPref = 1
GROUP BY c.Zip, c.State) AS 'Column Name' INTO #TempTable1
This is the error I see,
Msg 116, Level 16, State 1, Line 129
Only one expression can be specified in the select list when the subquery is not introduced with EXISTS.
Any pointers will help. Thanks.

Answer 1

I think you are making this much more complicated than it needs to be -- the first query can be written as
SELECT COUNT(DISTINCT c.CustomerNumber)
FROM Customer c
INNER JOIN TransactionDetail t ON c.CustomerNumber = t.CustomerNumber
WHERE
c.ProductXPref = 1 --Indicates if Customer was part of ProductX promotion program.
AND t.TransactionDate > DATEADD(d, -60, getdate()))
AND t.ProductXIndicator <> 1
As you can see if you just don't include these rows in the original count it is the same as doing another query and subtracting.
So the second is simply
SELECT c.Zip, c.State, COUNT(DISTINCT c.CustomerNumber)
FROM Customer c
INNER JOIN TransactionDetail t ON c.CustomerNumber = t.CustomerNumber
WHERE
c.ProductXPref = 1 --Indicates if Customer was part of ProductX promotion program.
AND t.TransactionDate > DATEADD(d, -60, getdate()))
AND t.ProductXIndicator <> 1
GROUP BY c.Zip, c.State

Answer 2

This should work:
SELECT
c.Zip, c.State,COUNT (DISTINCT c.CustomerNumber)
FROM
Customer c
INNER JOIN TransactionDetail t
ON
c.CustomerNumber = t.CustomerNumber AND
c.ProductXPref = 1 --Indicates if Customer was part of ProductX promotion program.
AND t.TransactionDate > DATEADD(DD, -60, getdate())
WHERE t.ProductXIndicator <> 1
GROUP BY c.Zip, c.State

Answer 3

after some validation the numbers did not match what I expect those to be, hence I have tried different logic which worked fine and returned what I wanted. So posting the answer here, again thanks for all the help.
SELECT d.State, d.Zip, COUNT(DISTINCT(d.CustomerNumber)) AS 'Active Customers'
INTO #ProductDifference
FROM Customer c
INNER JOIN
TransactionDetail t
ON
c.CustomerNumber = t.CustomerNumber
WHERE d.ProductXPref = 1
AND t.TransactionDate > DATEADD(d, -60, getdate())
AND c.CustomerNumber
NOT IN
(SELECT DISTINCT d.[CustomerNumber]
FROM Customer d
INNER JOIN
TransactionDetail f
ON
d.CustomerNumber = f.CustomerNumber
WHERE f.ProductXIndicator = 1
AND f.TransactionDate > DATEADD(DD, -60, getdate())
AND d.ProductXPref = 1)
GROUP BY c.State, c.Zip