Left Outer Join Question

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От Edward Murray
Тема Left Outer Join Question
Дата
Msg-id a5hmq8$6qi$1@jupiter.hub.org
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Ответы Re: Left Outer Join Question  ("Christopher Kings-Lynne" <chriskl@familyhealth.com.au>)
Re: Left Outer Join Question  (Stephan Szabo <sszabo@megazone23.bigpanda.com>)
Список pgsql-sql
I seem to have reached the limits of my (postgres)SQL knowledge. If
anybody could help me out of this predicament it would be greatly
appreciated. I know the explanation of this problem may seem a bit complex
but I am hoping the answer may be quite simple.

I have items represented for sale on a web-site. I have a number of
sections which each have sub-categories under them and each category may
contain items.

Each item is posted by a shop with a client number.

I am trying to list the sub-categories of a section and the number of
items posted in by a particular shop in each of those categories.

Simplified versions of the tables are as such:

sections (recordnum intname varchar
)

category (recordnum intname varchar
)



section_subcats (sectionum intcatnum int
)

items (recordnum intcatnum intclientnum intname varchar
)

The categories are assigned to the sections via the Section_subcats table
using data in the tables as such:


section
1     Fruit

category
1    Apple
2    Pear
3    Orange


section_subcats
1    1
1    2
1    3

items
1    1    333    'Jonathan'
2    1    333    'Fuji'
3    1    444    'Granny Smith'
I am trying to construct a query which will return something like the
following for clientnum 333:


Fruit
-----
Apple     2
Pear     0
Orange    0

I have tried the following query but the results with no items are
excluded:

select category.name, count(items.recordnum) from category left outer join
items on (category.recordnum = items.catnum) where category.recordnum =
section_subcats.catnum and section_subcats.sectionnum = 1 and
items.clientnum = 333 group by category.name;

Somebody Please Help!

Regards
Ed Murray
Avenue Network Services


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