It night use the index to find name, but the only way to find values in bitfield that match, with just an index on the value, is to scan through all the values. It can't assume that it only wants to find the value 0x0040, as that isn't the condition. Yes, if the cycles were added to ALL index searches, it could possibly do some proofs and determine the lowest value it could be would be 0x0040 and skip over to find that. and when it gets to 0x007F skip to 0x00C0, but that is a lot of logic for a very special case. Add a partial index on "B(name) where bitfield & 0x0040 != 0" might be good enough to get it to use the index. Of course, you will need to make a partial index for every bit combination you want to test. Making it a partial index cuts down the work to keep them, but does say you can't look for the converse condition of WHERE B.name=? AND B.bitfield & 0x0040 == 0 For that, you would need to make an index on B(name, bitfield&0x0040), and for all other bits you need, which gets to be a lot of index data.