Adding multiple results form multiple subqueries - sql

Question

I am running a SQL Server query to get the sum of the transaction amount and the pending amount and the extra amount. I found that the best solution to do that is using subqueries, hence I am using subqueries for the same, which is the fastest way. However, although I can extract the amount from each subquery, I can't figure out how to add them together so I can sort by the total number.
Here's the current query:
SELECT
*, trans + pend + extra AS totalamount
FROM
(SELECT
(SELECT trnammt
FROM Tbl_Emi
WHERE Status IN ('N', 'P')
AND lastrecdate = (CAST(GETDATE() AS DATE))
AND CardNo = CardNo) AS TRANS,
(SELECT pendamt
FROM Tbl_Emi
WHERE Status IN ('N', 'P')
AND lastrecdate = (CAST(GETDATE() AS DATE))
AND CardNo = CardNo) AS PEND,
(SELECT extraamt
FROM Tbl_Emi
WHERE Status IN ('N', 'P')
AND lastrecdate = (SELECT MIN(lastrecdate) FROM Tbl_Emi)
AND CardNo = CardNo) AS EXTRA
FROM
Tbl_Emi) q
I need to add together trans and pend and extra to get 'totalamount'. SQL Server won't allow you to use simple syntax to do calculations on aliases, but I presume there's another way to do this?

Answer 1

Here are three problems I can readily see:
The subqueries are not aggregated, so if they return multiple rows, you will get an error.
The correlation conditions only refer to the subquery (so they are not really correlated).
The results could be NULL, so the sum would be NULL.
This version fixes these three problems:
SELECT e.*,
(COALESCE(trans, 0) + COALESCE(pend, 0) + COALESCE(extra, 0)) AS totalamount
FROM (
SELECT (
SELECT SUM(trnammt)
FROM Tbl_Emi e2
WHERE Status IN ('N','P')
AND lastrecdate = (CAST(GETDATE() AS DATE))
AND e2.CardNo = e.CardNo
) AS trans,
(
SELECT sum(pendamt)
FROM Tbl_Emi e2
WHERE Status IN ('N','P')
AND lastrecdate = (CAST(GETDATE() AS DATE))
AND e2.CardNo = e.CardNo
) AS pend,
(
SELECT sum(extraamt)
FROM Tbl_Emi e2
WHERE Status IN ('N','P')
AND lastrecdate = (SELECT MIN(lastrecdate) FROM Tbl_Emi)
AND e2.CardNo = e.CardNo
) AS extra
FROM Tbl_Emi e
) e

Answer 2

If you just want sum of trans + pend + extra you need to change the criteria part
SELECT CASE WHEN (lastrecdate = (CAST(GETDATE() AS DATE))
AND CardNo = CardNo) THEN trnammt
ELSE 0
END +
CASE WHEN (pendamt = (CAST(GETDATE() AS DATE))
AND CardNo = CardNo) THEN trnammt
ELSE 0
END +
CASE WHEN (lastrecdate = (SELECT MIN(lastrecdate) FROM Tbl_Emi)
AND CardNo = CardNo) THEN trnammt
ELSE 0
END AS totalamount
WHERE Status IN ('N','P')