Humans
do not come with good natural primary keys. Names are not unique and they
change over time. In the USA we have a Social Security number which is
tempting to use as a primary key. Do not use it! They make rotten primary
keys for several reasons:
-
Not everyone
has one.
-
Some people
have two (or more).
-
Some numbers
are used by multiple people. (Not suppose to happen, but it does.)
-
Many people
think using the SSN is a civil liberties issue. They resent giving them
out. They may choose not to give it to you. They may give you an incorrect
one.
-
It is easy to
forge.
-
In most cases,
Federal law requires you to issue an alternative id to people who object
to giving you their SSN. (For extra credit, register at your local Community
College and refuse to give them your SSN. Can they cope? I did and mine
can.)
So do everyone
a favor and don't use the SSN as a primary key. If you need to store it,
do so in a column that isn't the primary key.
PS. An exceptionally
poor idea used by some banks and credit bureaus is to use the husband's
SSN to record a couple's credit history. What will they do if they
divorce?