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* replace_matches does not return {null}
@ 2011-02-22 11:25 Andreas Gaab <A.Gaab@scanlab.de>
0 siblings, 1 reply; 2+ messages in thread
From: Andreas Gaab @ 2011-02-22 11:25 UTC (permalink / raw)
To: pgsql-sql
Hi,
I tried to order a text-column only by parts of the entries. Therefore I used regexp_matches(), but unfortunately I am loosing rows.
SELECT regexp_matches('abc','[0-9]+'), regexp_matches('123','[0-9]+');
Does not return "{null}, {123}" but no result at all.
Is this behavior expected? How can I work around?
I am running postgres 8.4
Andreas
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^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: replace_matches does not return {null}
@ 2011-02-22 16:39 Tom Lane <tgl@sss.pgh.pa.us>
parent: Andreas Gaab <A.Gaab@scanlab.de>
0 siblings, 0 replies; 2+ messages in thread
From: Tom Lane @ 2011-02-22 16:39 UTC (permalink / raw)
To: Andreas Gaab <A.Gaab@scanlab.de>; +Cc: pgsql-sql
Andreas Gaab <A.Gaab@scanlab.de> writes:
> I tried to order a text-column only by parts of the entries. Therefore I used regexp_matches(), but unfortunately I am loosing rows.
> SELECT regexp_matches('abc','[0-9]+'), regexp_matches('123','[0-9]+');
> Does not return "{null}, {123}" but no result at all.
Yes, because regexp_matches returns a rowset of zero or more results.
The fine manual suggests putting it in a sub-select if what you want
is a null or a single result:
SELECT ... , (SELECT regexp_matches(...)) FROM ...
regards, tom lane
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2011-02-22 11:25 replace_matches does not return {null} Andreas Gaab <A.Gaab@scanlab.de>
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