Sometimes NULL values are given in tables, this might be
because the data is unknown or is inappropriate. In the
Parliament database a NULL value for party
in the MSP table
indicates that the MSP concerned is not a member of any of the
parties. In the party table a NULL value is used where
the party
does not have an official leader - or I couldn't find one. I
rather like it that the Greens and the Scottish Socialist Party
don't seem to have leaders - and it suits my purposes.
We can use the phrase
IS NULL
to pick out fields. We can use
IS NOT NULL similarly.
1. The parties which do not have a leader recorded.
