Question

I have two simple columns: datetime PayDate and int Amount
I tried to write a query that separate count of Amount per day but it doesnt work.

SELECT YEAR(PayDate) + '/' + MONTH(PayDate) + '/' + DAY(PayDate) as a,
COUNT(Amount) as b
FROM TABLE1
GROUP BY a,b

Thank you for help.

Answer 1

Why are you bothering with all this messy string concatenation? Format on the client if you want a specific output. Use base types instead of strings where possible.

SELECT CONVERT(DATE, PayDate) AS a, COUNT(Amount) AS b
FROM dbo.TABLE1
GROUP BY CONVERT(DATE, PayDate);

If you have a justified complex expression, the easiest way to avoid repeating it is to use a subquery or CTE:

SELECT a, COUNT(b) FROM
(SELECT CONVERT(DATE, PayDate) AS a, Amount AS b FROM dbo.TABLE1) AS x
GROUP BY a;

-- or

WITH x(a,b) AS
(SELECT CONVERT(DATE, PayDate), Amount FROM dbo.TABLE1)
SELECT a, COUNT(b) FROM x
GROUP BY a;

(I have no idea why you are grouping by both a and b in your question.)