Re: back references using regex

Thanks. I'll check it out asap. I didn't realize the
regex expressions needed to be escaped for it to be a
valid expression. I thought it was the other way
around. Would it be possible to choose what paragraph
to use in a summary? I'll try to clarify... Let's say
I have 14 paragraphs of lorem lipsum text. Let's say I
want to show the 3rd paragraph... Could I use a regex
to search the content and return that 3rd paragraph to
use as a summary of that article?

--- Michael Fuhr <mike(at)fuhr(dot)org> wrote:

> On Tue, Sep 06, 2005 at 11:40:18PM -0700, Matthew
> Peter wrote:
> > I'm trying to do a slice directly from a table so
> I
> > can get a brief preview of the articles content by
> > counting \s (spaces), not new paragraphs.
>
> Are you trying to extract the first N words from a
> string? If
> that's not what you mean then please clarify.
>
> > Anyone know how it could be done using regular
> > expressions natively? I read the doc but it didn't
> > help me much.
>
> Regular expressions aren't the only way to solve the
> problem, but
> maybe the following example will give you some
> ideas:
>
> CREATE TABLE article (id integer, content text);
>
> INSERT INTO article VALUES (1, 'one');
> INSERT INTO article VALUES (2, 'one two');
> INSERT INTO article VALUES (3, 'one two three');
> INSERT INTO article VALUES (4, 'one two three
> four');
> INSERT INTO article VALUES (5, 'one two three four
> five');
> INSERT INTO article VALUES (6, 'one two three four
> five six');
>
> SELECT id, substring(content FROM
> '(([^[:space:]]+[[:space:]]*){1,3})')
> FROM article;
> id | substring
> ----+----------------
> 1 | one
> 2 | one two
> 3 | one two three
> 4 | one two three
> 5 | one two three
> 6 | one two three
> (6 rows)
>
> In PostgreSQL 7.4 and later you could shorten the
> regular expression:
>
> SELECT id, substring(content FROM
> '((\\S+\\s*){1,3})')
> FROM article;
>
> If this example isn't what you're looking for then
> please explain
> what you're trying to do.
>
> --
> Michael Fuhr
>

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