Você poderia apenas fazer o seguinte?
SELECT
*
FROM
Table
WHERE
(@booleanResult = 1
AND Column1 = 'value1')
OR
(@booleanResult = 0
AND Column1 = 'value1'
AND Column2 = 'value2')
SELECT
*
FROM
Table
WHERE
(@booleanResult = 1
AND Column1 = 'value1')
OR
(@booleanResult = 0
AND Column1 = 'value1'
AND Column2 = 'value2')