[wvenable]

I finally got our company to standardize on someone's employee number as a primary key for everything employee related. It's a simple monotonically increasing integer value -- the best possible primary key.

We moved to a new HR system and they have a set of "reserved" employee numbers that cannot be used and we have employee numbers in that range. Arg!

[robaato]

We had a classic situation at a software house I worked at in the '80s - employee numbers were 1-999 and then jumped to 5,000 - because, you guessed it, this "unique" field was used with magic numbers 1,000 - 5,000 being reserved for project ids in various key accounting systems!

And we were supposed to teach our customers good design principles...