Michael Glaesemann wrote:
On Jan 24, 2006, at 20:00 , Alban Hertroys wrote:
Though this does give the right results, I would have liked to be
able to use NOT HAVING. Or is there a way using HAVING that would
give the same results? I'm quite sure HAVING sort_order <> 1 doesn't
mean the same thing.
Why are you so sure? It seems to me that NOT HAVING sort_order = 1 and
HAVING sort_order <> 1 would mean semantically the same thing. Can you
show that HAVING sort_order <> 1 gives incorrect results?
There's a difference in meaning. By NOT HAVING sort_order = 1 I mean
there is no record in the grouped records that has sort_order = 1. In
contrast HAVING sort_order <> 1 means there is a record in the group
with a sort_order other than 1, even if there's also a sort_order = 1 in
the grouped records.
To illustrate, say we have sort_orders 1,2,3,4,5:
- NOT HAVING sort_order = 1 would result false
- HAVING sort_order <> 1 would result true
If we'd have 2,3,4,5:
- NOT HAVING sort_order = 1 would result true
- HAVING sort_order <> 1 would result true
If we'd have 1 only:
- NOT HAVING sort_order = 1 would result false
- HAVING sort_order <> 1 would result false
But it seems HAVING can't be applied to columns not in the group by or
an aggregate. No idea why that might be...
--
Alban Hertroys
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