"Karen Hill" <[EMAIL PROTECTED]> 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
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