[gfody]

beg pardon I wasn't aware sql actually defined empty. of the engines I'm familiar with there is no keyword for empty like what gp is asking for (and I hold my argument for why it should not be necessary). it sounds like what you're describing is a blank string and I agree with using blanks to distinguish between "has no phone number" and "we don't know their phone number" but that isn't what gp was talking about.