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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