Hello Again: I'm trying to do some clinical research on large data sets and I ran into a problem represented in the following simplified example: geo-> select * from test2; +-----------+-----------+ | a | b | +===========+===========+ | 3.05 | 3.07 | | 3.06 | 3.04 | | 3.13 | 3.16 | | 3.22 | 3.22 | | 3.05 | 3.05 | | 3.07 | 3.06 | | 3.08 | 3.05 | | 3.12 | 3.09 | | 3.20 | 3.17 | | 3.17 | 3.20 | | 3.09 | 3.11 | | 2.74 | 2.73 | | 2.79 | 2.78 | | 2.80 | 2.81 | +-----------+-----------+ 14 rows geo-> select * from test2 where a=b; +-----------+-----------+ | a | b | +===========+===========+ | 3.22 | 3.22 | | 3.05 | 3.05 | +-----------+-----------+ 2 rows geo-> select * from test2 where (a/b)-1=0; +-----------+-----------+ | a | b | +===========+===========+ | 3.06 | 3.04 | | 3.22 | 3.22 | | 3.05 | 3.05 | | 3.07 | 3.06 | | 3.08 | 3.05 | | 3.12 | 3.09 | | 3.20 | 3.17 | | 2.74 | 2.73 | | 2.79 | 2.78 | +-----------+-----------+ <>9 rows geo-> select * from test2 where (b/a)-1=0; +-----------+-----------+ | a | b | +===========+===========+ | 3.05 | 3.07 | | 3.13 | 3.16 | | 3.22 | 3.22 | | 3.05 | 3.05 | | 3.17 | 3.20 | | 3.09 | 3.11 | | 2.80 | 2.81 | +-----------+-----------+ <>7 rows I thought that if a=b, then (a/b)-1 and (b/a)-1 must both also be equal to 0. Columns a and b are type decimal(7,2) and the data was entered to two decimal places by hand using insert statements. Thanks and best.......George ge I