The remaining options are a single consolidated column like bitfield flags or a boolean column per chain. I'm not sure what factorial planet davinci was on but the way you normally do it is allocate each bit to a flag. so 1 = bitcoin, 2=namecoin, 4=scamcoin. Then each is easy to extract with a simple logical &.
That was my original suggestion you shot down as too complex! Jack bean stalk!
what i did not know is you could do this in SQL...
select * from shares where reason IS NULL and chainmask & 2;
instead of this...
select * from shares where reason IS NULL and chainmask in (2, 3, 6, 7, 10, 11, 14, 15);
So I was on the SQL ignorance planet! My problem is I don't think of SQL as a computer language, I think of it as a bad hack for accessing data and thus forget how robust it is.
OH well. Learn something new everyday.
Anyhow...
I say having more than 32 block chains is crazy so unsigned INT is the way to go.
Thus my vote is for a bit wise column!
Davinci