>>>

when a=1 and b=1 then 100 else when a=1 and  b=0 then 50 ...

>>
>>Yep, Unfortunately T-SQL doesn't have logical data type
>
>Which is kind of ridiculous, because it has the bit type as a field. It's just that it treats it as unusable in expressions, unless you cast it as a, say, integer.

Bit is numeric data type but not numeric enough to be used in numeric expressions. At the end it's not numeric or logical for practical purpose