Andrius,
see the explanation about that at
http://www.postgresql.org/docs/8.3/static/functions-comparison.html for
more details.
Cheers
Julo
Heikki Linnakangas wrote:
Andrius Glozeckas wrote:
I have a parent_type_id linking to group_type_id on the same table
(group_type). I am trying to get the groups with certain
parent_type_id (be
it null or 17) and the number of their children in the same query:
SELECT g1.*, COUNT(g2.*)
FROM group_type g1 LEFT JOIN group_type g2 ON g1.group_type_id =
g2.parent_type_id
WHERE g1.parent_type_id = null GROUP BY g1.name, g1.type, g1.choice,
g1.multiple, g1.self_ref,
g1.group_type_id, g1.parent_type_id
But this doesn't give me any results, although there are a few
records with
parent_type_id = null and one with 17. I have tried a simpler query:
SELECT g1.*, g2.* FROM group_type g1 LEFT JOIN group_type g2 ON
g1.group_type_id = g2.parent_type_id WHERE g1.parent_type_id = null
This again doesn't give me any results
If I take the WHERE off, I get a list as expected with several
g1.parent_type_id = null
Use the IS NULL operator, instead of "= NULL", for testing if a column
is null: "WHERE gl.parent_type_id IS NULL". This is a basic SQL thing,
not a bug.
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