Mike C (4/14/2010)
I wouldn't expect many collisions with MD5 unless you're processing 2^64 or more rows. If you're getting collisions with MD5 or SHA I would immediately suspect the concatenation function you're using.
Ha! I apologize. Not sure why, but I was thinking CRC32 this entire time. MD5 and SHA1 both work great. CRC32 will result in collisions.