Re: execute same query only one time? - Mailing list pgsql-general

Am 08.02.2016 um 20:15 schrieb David G. Johnston:
> On Mon, Feb 8, 2016 at 12:05 PM, Johannes <jotpe@posteo.de> wrote:
>
>> Hi,
>>
>> is there a best practice to share data between two select statements?
>>
>> 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;
>
>
> Please confirm:​
>
> ​You want the​ result of "SELECT max(id) FROM t0" to be used in the second
> query without having to recompute it?

Yes.

> What client are you using to execute these statements?

JDBC. I execute both statements at once and iterate through the resultsets.

Johannes