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In TSql, how do you turn off a specific bit in a bitmask without having to check to see if the bit is set or not?
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Use the bitwise AND operator (&) to clear a bit. number &= ~(1 << x); That will clear bit x. You must invert the bit string with the bitwise NOT operator (~), then AND it.
The idea is to use bitwise <<, & and ~ operators. Using expression “~(1 << (k – 1))“, we get a number which has all bits set, except the k'th bit. If we do bitwise & of this expression with n, we get a number which has all bits same as n except the k'th bit which is 0.
Bit masks are used to access specific bits in a byte of data. This is often useful as a method of iteration, for example when sending a byte of data serially out a single pin. In this example the pin needs to change its state from high to low for each bit in the byte to be transmitted.
Found it! Use & ~ like this...
UPDATE MyTable SET MyBitmask = MyBitmask & ~128 -- 8th bit WHERE MyID = 123 The ~ operator flips all the bits (1s become 0s and 0s become 1s). Just set the value that you flip to the one you want to turn off and use & to safely turn off just the one specific bit without having to check to see if the bit is set.
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