Multiplier les valeurs des lignes revient à ajouter les logarithmes des valeurs des lignes
L'astuce consiste à gérer les zéros et les valeurs nulles.
Ok, vérifié maintenant
DECLARE @foo TABLE (GrpID varchar(10), Value float)
INSERt @foo (GrpID, Value)
SELECT 'Grp1', 2
UNION ALL SELECT 'Grp1', 5
UNION ALL SELECT 'Grp1', 3
UNION ALL SELECT 'Grp2', 3
UNION ALL SELECT 'Grp2', -5
UNION ALL SELECT 'Grp2', -2
UNION ALL SELECT 'Grp3', 4
UNION ALL SELECT 'Grp3', 0
UNION ALL SELECT 'Grp3', 1
UNION ALL SELECT 'Grp4', -2
UNION ALL SELECT 'Grp4', -4
UNION ALL SELECT 'Grp5', 7
UNION ALL SELECT 'Grp5', NULL
UNION ALL SELECT 'Grp6', NULL
UNION ALL SELECT 'Grp6', NULL
UNION ALL SELECT 'Grp7', -1
UNION ALL SELECT 'Grp7', 10
SELECT
GrpID,
CASE
WHEN MinVal = 0 THEN 0
WHEN Neg % 2 = 1 THEN -1 * EXP(ABSMult)
ELSE EXP(ABSMult)
END
FROM
(
SELECT
GrpID,
--log of +ve row values
SUM(LOG(ABS(NULLIF(Value, 0)))) AS ABSMult,
--count of -ve values. Even = +ve result.
SUM(SIGN(CASE WHEN Value < 0 THEN 1 ELSE 0 END)) AS Neg,
--anything * zero = zero
MIN(ABS(Value)) AS MinVal
FROM
@foo
GROUP BY
GrpID
) foo
