SELECT * 
FROM Bookings 
WHERE Resource = 'I' AND ( ([Date] = '2001-10-05' AND 
UPPER([Freq]) = 'S') OR (UPPER([Freq]) <> 'S' AND '2001-10-05' 
<= [EndDate]) )

when you change the SQL to this it works

SELECT * 
FROM Bookings 
WHERE Resource = 'I' AND ( ([Date] = '2001-10-05' AND 
UPPER([Freq]) = 'S') OR (UPPER([Freq]) <> 'S' AND  [EndDate] 
>= '2001-10-05') )

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 Comments and Workarounds

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DBISAM internally flips all expressions where the constant is on the left-hand side to the right-hand side, but it was not flipping around the <= operator properly along with the <, >, >= operators. The workaround is to flip the expression around manually so that the constant is on the right-hand side of the binary operation.

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 Resolution

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Fixed Problem on 10/4/2001 in version 2.12 build 1