In article <20080627075136.12add021@dick.coachhouse>,
Tarlika Elisabeth Schmitz <postgresql@numerixtechnology.de> writes:
> PRODUCT table :
> A B C
> 100 200 300
> 100 200 301
> 100 205 300
> 100 205 301
> NAVIGATION table
> A B C #ITEMS
> 100 200 300 5
> 100 200 301 6
> My query needs to return
> 100 205 300 #items
> 100 205 301 #items
> so I can insert them in NAVIGATION. NAVIGATION must not contain any
> duplicate combinations of [a,b,c].
Just use another LEFT JOIN to filter out the corresponding product lines:
SELECT DISTINCT a, b, c, now(), count(item_pk)
FROM product
LEFT JOIN navigation USING (a, b, c)
LEFT JOIN item ON item.product_fk = product_pk
WHERE navigation.a IS NULL
GROUP BY a, b, c