Kevin Loney once gave an excellent talk, "Controlled Flight into Terrain", at an Oracle users group conference. As I recall, one of the cases he mentioned of se

Kevin Loney once gave an excellent talk, "Controlled Flight into Terrain", at an Oracle users group conference. As I recall, one of the cases he mentioned of self-inflicted damage involved the company that wanted strict, gapless order for an ID column. It would have been entirely possible to avoid ID conflicts by using the INCREMENT BY feature of Oracle sequences, but the company had European systems fetching the next ID value from a server in the US. I sympathize with customers who don't expect gaps of 20 (Oracle) or 32 in ID sequences. But the relational model is one of unordered tuples, isn't it?