Re: order of (escaped) characters in regex range

On Dec 13, 2011, at 8:09, Szymon Guz <mabewlun(at)gmail(dot)com> wrote:

>
>
> On 13 December 2011 14:04, InterRob <rob(dot)marjot(at)gmail(dot)com> wrote:
> Dear List,
>
> I found this interesting:
>
> SELECT regexp_matches('123-A' , E'(3[A-Z\- ])');
> ERROR: invalid regular expression: invalid character range
>
> whereas:
> SELECT regexp_matches('123-A' , E'(3[\- A-Z])');
> regexp_matches
> ----------------
> {3-}
> (1 row)
>
> Notice the order of (escaped) characters and ranges in the last bit of the expression.
>
> Am I missing some key concept of the regular expression?
>
> Regards,
> Rob
>
> Hi Rob,
> try '\\-' instead of '\-'
> and it works :)
>
> regards
>

If you don't intend to use PostgreSQL escapes in your string then omit the leading 'E'.

In a character class the - symbol has special meaning if it appears anywhere but the first character of the group. To avoid that special meaning you have to escape it. If it appears first it always means a literal -. The PostgreSQL documentation does not fully describe RegularExpressions but a reference book on them would note this particular behavior.

David J.