He was using MD5 and then only used the 8 first (or last) characters. This can lead to collisions.

(Also in theory two MD5s from two different inputs can be identical, but this is very unlikely)

In reply to Re^4: Question: Generate unique/random 12-digit keys for 25,000K records, howto?? by mscharrer
in thread Question: Generate unique/random 12-digit keys for 25,000K records, howto?? by lihao

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