From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200511291613.jATGDnm08350@candle.pha.pa.us>
Subject: Re: 'AS' in 'DELETE/UPDATE'
In-Reply-To: <902550887.20051129210156@hlebprom.ru>
To: engineer@hlebprom.ru
Date: Tue, 29 Nov 2005 11:13:49 -0500 (EST)
CC: pgsql-sql@postgresql.org
MIME-Version: 1.0
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TODO has:

        o Allow an alias to be provided for the target table in
          UPDATE/DELETE

          This is not SQL-spec but many DBMSs allow it.

so we want to add this capability some day.

---------------------------------------------------------------------------

engineer@hlebprom.ru wrote:
> Hi.
> 
> Maybe I miss something but I can't use 'AS' with 'DELETE' (7.4.3)
> Example:
> 
> db=# SELECT * FROM temp1 ;
>  host_id | user_id | raw | uniq
> ---------+---------+-----+------
>        2 |       1 | 125 |   85
>        2 |       2 | 100 |   50
> (2 rows)
> 
> And there is temp2 just like temp1.
> 
> db=# DELETE FROM temp1 AS t1 WHERE EXISTS (SELECT 1 FROM temp2 AS t2
> WHERE t2.host_id = t1.host_id AND t2.user_id = t1.user_id); 
> ERROR:  syntax error at or near "AS" at character 19
> 
> but
> 
> db=# DELETE FROM temp1 WHERE EXISTS (SELECT 1 FROM temp2 AS t2 WHERE
> t2.host_id = temp1.host_id AND t2.user_id = temp1.user_id); 
> DELETE 1
> db=# SELECT * FROM temp1 ;
>  host_id | user_id | raw | uniq
> ---------+---------+-----+------
>        2 |       1 | 125 |   85
> (1 row)
> 
> It make me supply full name of table...
> 
> 
> Another example with UPDATE
> 
> db=# UPDATE referer_total AS ref SET ref.raw = ref.raw + u.raw,
>      ref.uniq = ref.uniq + u.uniq FROM temp1 AS u
>      WHERE u.user_id = ref.user_id AND ref.referer = u.referer;
> ERROR:  syntax error at or near "AS" at character 22
> 
> db=# UPDATE referer_total SET
> db-#        referer_total.raw = referer_total.raw + u.raw,
> db-#        referer_total.uniq = referer_total.uniq + u.uniq
> db-# FROM temp1 AS u WHERE u.user_id = referer_total.user_id
> db-# AND referer_total.referer = u.referer;
> ERROR:  syntax error at or near "." at character 46
> 
> So it make me rename temp1's "raw" to something else ("r"), "uniq"
> too; and 'AS' not possible too. And finally, working version:
> 
> UPDATE referer_total SET raw = raw + r, uniq = uniq + u
> FROM temp1 AS u WHERE
> u.user_id = referer_total.user_id AND
> referer_total.referer = u.referer;
> 
> 
> It looks strange, are there any limitations or something else that
> make it not possible to use 'AS' in 'DELETE' and 'UPDATE'? Of course
> with described workarounds I can eliminate that problems, but I want
> to know is it so in 8.x? Or why, if it right behaviour?
> 
> -- 
> engineer
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
> 

-- 
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