One problem I've run into with char(1) for this is that some clever developer somewhere along the way inevitably wants to put T/F in a column that also has Y/N, and even 1/0 (as characters). Suddenly, querying becomes really, really interesting. Check constraints can help with that.
Also takes up more space (disk and RAM) than bit. (If you have 8 bit fields per row, that's the same amount of disk/RAM as 1 char(1) field.)
In my old app that was Access on top of SQL, checkboxes worked with the bit data type, but not with Y/N or T/F char fields (of course), so another point becomes, will the front end app have to translate these, or will it deal with it more gracefully? Most app dev languages deal with 1/0 for that kind of thing more easily than with character data.
- Gus "GSquared", RSVP, OODA, MAP, NMVP, FAQ, SAT, SQL, DNA, RNA, UOI, IOU, AM, PM, AD, BC, BCE, USA, UN, CF, ROFL, LOL, ETC
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