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Posted by David Portas on 11/16/05 15:11
Jens wrote:
> Hi Kal,
>
>
> You sure should handle the situation that the thing you are
> substracting runs out of stocks, but the query should be:
>
> UPDATE product
> SET quantity = quantity - c.quantity
> FROM product p
> INNER JOIN Cart c
> ON p.productid=c.productid
>
>
> HTH, Jens Suessmeyer.
Jens,
I think diablo will want to add "WHERE c.buyerid=x" to your query. Even
then the quantity value will not be correctly updated unless
(buyerid,productid) is unique, which it may be, although that wasn't
explicitly stated.
Diablo,
Please include DDL with future posts (CREATE TABLE, with keys and
constraints) then we don't have to makes guesses about your tables.
--
David Portas
SQL Server MVP
--
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