Ron Johnson <ron.l.johnson@xxxxxxx> writes: > On 11/23/07 03:33, Peter Childs wrote: >> The worse thing I meet is people who think primary keys need to be >> integer single field unique serial fields >> >> I tend to agree that primary keys should be single fields if they need >> to be referenced but should also be natural if at all possible. ie use >> car number plates rather than some serial int. > I wouldn't trust plate number to be unique over time, since the > format "ABC 123" only has a capacity of 17,576,000 vehicles. There's a worse problem than that: what if you find out that you mis-entered the value? Now you have to change the record's primary key in order to stay consistent with the real world. Which is exactly what a primary key should never have to do, at least in the opinion of those who recommend synthetic primary keys. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
