Re: execute same query only one time?

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