Compare with CHAR

Hi.

I'm using a table with a indexed CHAR(3)-column. When I use SELECT .. WHERE
Col = 'XXX', some results are empty, but the value in the row seems to be
correct like other rows. If I update the row with same data I can get it
into the result. So I didn't find any logic reason for this. I can find all
rows using LIKE (or with some substring tests) with no problems. Shouldn't =
always works the same..? (Postgres 7.1.3)

kind regards
Tomas