Обсуждение: HELP with a Query

Hi,
I need some help with a query.
I use a reference table to lookup some codes. Everything works well if the reference table contains a reference but the
queryfails if no reference fails (Z.ref_code=123456).  
What I need to is either return 0 or null into Z.prim_exch if no reference can be found. Whats the best way to do that
?I tried a sub query but also did not succeed. 


SELECT A.sec_code,A.exch_code,A.price_date,Z.prim_exch,
   CASE
     WHEN A.exch_code = Z.prim_exch THEN 1
     ELSE 0
   END AS is_prim
FROM price_hist AS A, references AS Z
WHERE   A.price_date <= '20040219' AND A.sec_code=123456 AND Z.ref_code=123456 LIMIT 10;

Thanks for any help.
Alex

On Sat, Feb 21, 2004 at 05:20:51PM +0900, Alex wrote:
> Hi,
> I need some help with a query.
> I use a reference table to lookup some codes. Everything works well if the
> reference table contains a reference but the query fails if no reference
> fails (Z.ref_code=123456). What I need to is either return 0 or null into
> Z.prim_exch if no reference can be found. Whats the best way to do that ? I
> tried a sub query but also did not succeed.

Lookup an SQL site about OUTER JOINS. Should do what you want.

--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
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