On 7 Aug 2010, at 23:18, Thomas Kellerer wrote:
> Or as an alternative:
>
> SELECT tid, purchase_date
> FROM orders
> WHERE item in ('Laptop', 'Desktop')
> GROUP BY tid, purchase_date
> HAVING count(*) = 2
This one is incorrect, it will also find people who bought two laptops or two desktops on the same date.
I was going to suggest:
SELECT tid, "date", 001::bit as type
FROM orders
WHERE item = 'Laptop'
UNION ALL
SELECT tid, "date", 010::bit as type
FROM orders
WHERE item = 'Desktop'
GROUP BY tid, "date"
HAVING type & 011::bit = 011::bit;
But I think David's solution is more readable, as it leaves the item names in tact.
Alban Hertroys
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