SELECT
[qid1].AgeBelow16 - [qid2].AgeBelow16 AS [AgeBelow16],
[qid1].Age16_20 - [qid2].Age16_20 AS [Age16_20],
[qid1].Age21_30 - [qid2].Age21_30 AS [Age21_30],
[qid1].Age31_40 - [qid2].Age31_40 AS [Age31_40],
[qid1].Age41_50 - [qid2].Age41_50 AS [Age41_50],
[qid1].Age51_60 - [qid2].Age51_60 AS [Age51_60]
FROM
MyTable AS [qid1]
INNER JOIN
MyTable AS [qid2]
ON [qid1].QID = [qid2].QID - 1
WHERE
[qid1].QID = 1
Om möjligt skulle du dock vara mycket bättre att lagra QID2-värdena som negativa. På så sätt behöver du inte veta vilken du ska subtrahera från den andra; det är bara en rak SUMMA.
SELECT
SUM(AgeBelow16) AS [AgeBelow16], -- (93) + (-13) = 80
SUM(Age16_20) AS [Age16_20], -- (81) + (-11) = 70
SUM(Age21_30) AS [Age21_30], -- (55) + (-15) = 40
SUM(Age31_40) AS [Age31_40], -- (46) + (-16) = 30
SUM(Age41_50) AS [Age41_50], -- (54) + (-14) = 40
SUM(Age51_60) AS [Age51_60] -- (48) + (-18) = 30
FROM
MyTable