From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Edson Richter <edsonrichter(at)hotmail(dot)com> |
Cc: | "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Trouble with regexp_matches |
Date: | 2016-11-05 17:21:07 |
Message-ID: | 31701.1478366467@sss.pgh.pa.us |
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Lists: | pgsql-general |
Edson Richter <edsonrichter(at)hotmail(dot)com> writes:
> I’m running the query below, and it is limiting results as if “regexp_matches” being in where clause.
> IMHO, it is wrong: in case there is no match, shall return null or empty array – not remove the result from the set!!!
Well, no, because regexp_matches() returns a set. If there's no match,
there's zero rows in the set.
The standard workaround is to use a scalar sub-select, which has the
effect of converting a zero-row result into a NULL:
select codigoocorrencia, datahoraocorrencia, datahoraimportacao,
observacao, (select regexp_matches(observacao, '\d\d/\d\d/\d\d\d\d'))
from ...
As of v10 there will be a less confusing solution: use regexp_match()
instead.
regards, tom lane
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