First: Please don't reply to an existing message to create a new thread. Your mail client copies the replied-to message ID into the References: header, and well-implemented mail clients will thread your message under a now-unrelated thread.
Compose a new message instead. Marc Mamin wrote: > I have a string that contains a serie of chars, separated by single > spaces. > > e.g 'a b x n r a b c b' > > Having such a string, I d'like to get a list of all predecessors of a > given character. > In the example, the predecessors of b are a,a,c. OK, so wherever `b' occurs, you want the character at index `b -2'. > select regexp_matches('a a a', '([a-z]) a','g'); > => {"a "} only The issue is that regular expressions don't like to overlap matches. The first match consumes _two_ leading `a' characters. What you need is a zero-width lookahead assertion, available in Perl-style extended regular expressions. Handily, recent PostgreSQL versions support these, so you can write: test=> select regexp_matches( 'a a a', '([a-z]) (?=a)', 'g'); regexp_matches ---------------- {a} {a} (2 rows) -- Craig Ringer -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql