Re: execute same query only one time?

On 2/8/16, Johannes <jotpe@posteo.de> wrote:
>
> Am 08.02.2016 um 20:32 schrieb Vitaly Burovoy:
>> On 2/8/16, Adrian Klaver <adrian.klaver@aklaver.com> wrote:
>>> 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 ...);
>>
>> I don't think it is a good solution because it leads to copying
>> columns from the t0 which is wasting net traffic and increasing
>> complexity at the client side. Moreover it works iff t0 returns only
>> one row.
>
> I had same doubts.
> CTE would be first class, if it was be reusable for other statements.
>
> Johannes

CTEs are temporary tables for a _statement_ for using a single
statement instead of several ones (create temp table, insert into,
select from it, select from it, drop temp table).

But it is not your case because CTEs are for a queries which return a
single set of rows. Your case is returning two sets (one row with
several columns from t0 and several rows with a single columns from
t1).

--
Best regards,
Vitaly Burovoy