"Karen Hill" <karen_hill22@xxxxxxxxx> writes: > Ralph Kimball states that this is a way to check for changes. You just > have an extra column for the crc checksum. When you go to update data, > generate a crc checksum and compare it to the one in the crc column. > If they are same, your data has not changed. You sure that's actually what he said? A change in CRC proves the data changed, but lack of a change does not prove it didn't. People do sometimes use this logic in connection with much wider "summary" functions, such as an MD5 hash. I wouldn't trust it at all with a 32-bit CRC, and not much with a 64-bit CRC. Too much risk of collision. regards, tom lane
