From: | Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> |
---|---|
To: | Johannes <jotpe(at)posteo(dot)de>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: execute same query only one time? |
Date: | 2016-02-08 19:19:11 |
Message-ID: | 56B8EA2F.7010105@aklaver.com |
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Lists: | pgsql-general |
On 02/08/2016 11:05 AM, Johannes wrote:
> Hi,
>
> is there a best practice to share data between two select statements?
A join:
http://www.postgresql.org/docs/9.4/interactive/sql-select.html
Search for:
join_type
>
> Imaging following situation: I want to receive two result sets from two
> tables, referring to a specific id from table t0 AND I try not to query
> for that specific id a second time.
>
> Table t0 returns 1 row and table t1 returns multiple rows.
>
> begin;
> select id, col1, col2, ... from t0 where id = (select max(id) from t0
> where col1 = value1 and col2 = value2 and ...);
> select col1 from t1 where t0_id = (select max(id) from t0 where col1 =
> value1 and col2 = value2 and ...);
> commit;
Based on rough guess of the above, without seeing actual table schemas:
select id, t0.col1, t1.col1, col2, ... from t0 JOIN t1 ON t0.id =
t1.t0_id where id = (select max(id) from t0 where col1 = value1 and col2
= value2 and ...);
>
> Best regards Johannes
>
--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com
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