Yes, that does work, but only because id is NOT NULL. I thought Postgres 8.4 had had a load of these join types unified to make it less important how the query is written?
well, as a rule of thumb - unless you can't think of a default value of column - don't use nulls. So using nulls as default 'idunno' - is a bad practice, but everybody's opinion on that differ.
But back on a subject, postgresql is very very poor performance wise with [NOT] IN () type of constructs. So if you can, avoid them, and learn to use joins.
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GJ
