Re: Regexp confusion

Doug Gorley escribió:
> Trying to match some numbers, and I'm having some regexp problems.
> I've boiled it down to the following:
>
> /* (1) */ select '3.14' similar to E'^\\d+\\.\\d+$'; -- true
> /* (2) */ select '3.14' similar to E'^\\d+(\\.\\d+)$'; -- true
> /* (3) */ select '3.14' similar to E'^\\d+(\\.\\d+)*$'; -- true
> /* (4) */ select '3.14' similar to E'^\\d+(\\.\\d+)?$'; -- false
> /* (5) */ select '3.14' similar to E'^\\d+(\\.\\d+)+$'; -- true
>
> So, based on (1) and (2), the pattern '\.\d+' occurs once. So why
> does (4) return false? between (3), (4), and (5), it appears as
> though the group is matching multiple times.

I think the confusion is about what SIMILAR TO supports. ? it doesn't.
See here:
http://www.postgresql.org/docs/8.4/static/functions-matching.html#FUNCTIONS-SIMILARTO-REGEXP

You probably want to use ~ instead of SIMILAR TO.

(SIMILAR TO is a weird beast that the SQL committee came up with,
vaguely based on regular expressions.)

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Alvaro Herrera http://www.CommandPrompt.com/
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