Subquery in MySql group by

Question

I have a query:

SELECT round(addTime/qty, 0) AS col1,
       sum(qty) AS col2,
       cId AS Id
FROM MyTable
WHERE qty > 0
GROUP BY round(addTime/qty, 0), cId
ORDER BY round(addTime/qty, 0)

But I have to replace addTime with a

SUM(CASE WHEN qty = 1 THEN 1 ELSE DATEDIFF(second,startTime,endTime) END)/qty, 0)

And when I do this:

SELECT round(SUM(case when qty = 1 then 1 else DATEDIFF(second,startTime,endTime) end)/qty, 0) AS col1,
sum(qty) AS col2,
cId
FROM MyTable
WHERE qty > 0
GROUP BY round(SUM(case when qty = 1 then 1 else
DATEDIFF(second,startTime,endTime) end)/qty, 0)/qty, 0), cId
ORDER BY round(SUM(case when qty = 1 then 1 else DATEDIFF(second,startTime,endTime) end)/qty, 0)/qty, 0)

I get

Cannot use an aggregate or a subquery in an expression used for the group by list of a GROUP BY clause.

My idea was that I can use that new query as variable and then use it where I need but then I ran into trouble with MySql syntax.

Big thanks in advance!

Answer 1

Try it with a sub query in the from clause:

Select * from (select round(...) as col1 from MyTable) as tmp where ... Group By tmp.col1

Subqueries in from clause

Answer 2

SELECT *
FROM (
    SELECT 
        round(SUM(case when qty = 1 then 1 else DATEDIFF(second, startTime,endTime) end)/qty, 0) AS col1, 
        sum(qty) AS col2, 
        cId
    FROM MyTable
    WHERE qty > 0
) AS t
GROUP BY t.col1, t.cId
ORDER BY t.col1

Also I'm not sure, but your DIFFTIME function if different from MySQL DIFFTIME .