How to flip bit fields in T-SQL?

You don’t need a bitwise-not for this — just XOR it with 1 / true.

To check it:

select idColumn, bitFieldY, bitFieldY ^ 1 as Toggled
from tableX

To update:

update tableX
set bitFieldY = bitFieldY ^ 1
where ...

MSDN T-SQL Exclusive-OR (^)