What are the reasons *not* to use a GUID for a primary key?

Question

Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables)

I know I\'ll never lose

Answer 1

Simple answer: it's not relational.

The record (as defined by the GUID) may be unique, but none of the associated attributes can be said to be occuring uniquely with that record.

Using a GUID (or any purely surrogate key) is no more relational than declaring a flat file to be relational, on the basis that each record can be identified by its row number.