[firebird-support] SUM(DC.I) / SUM(DC.Q) vs SUM(DC.I / DC.Q) why result is different?

Hallo,
I have, in DC table, two rows with same data:
A_ID I Q
1 370 1
2 370 1

with this query:

SELECT FIRST 1
DT.D as DCU,
SUM(DC.I) / SUM(DC.Q) AS CU,
(SELECT
SUM(DC.I) / SUM(Q)
FROM
DOC_C DC
WHERE
DC.C > 0.00
AND DC.A_ID = :ID
) AS CM
FROM
DOC_C DC, DOC_T DT
WHERE
DC.DOC_T_ID = DT.ID
AND DC.C > 0.00
AND DC.A_ID = :ID
GROUP BY
DT.D
ORDER BY
DT.D

I obtain correct result:
CU = 370
CM = 370

but with this query:

SELECT FIRST 1
DT.D as DCU,
SUM(DC.I / DC.Q) AS CU,
(SELECT
SUM(DC.I) / SUM(Q)
FROM
DOC_C DC
WHERE
DC.C > 0.00
AND DC.A_ID = :ID
) AS CM
FROM
DOC_C DC, DOC_T DT
WHERE
DC.DOC_T_ID = DT.ID
AND DC.C > 0.00
AND DC.A_ID = :ID
GROUP BY
DT.D
ORDER BY
DT.D


I obtain wrong result:
CU = 740
CM = 370


Why?

What is the difference from "SUM(DC.I) / SUM(DC.Q)"
and "SUM(DC.I / DC.Q)"

Thanks
--
Luigi Siciliano
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