Re: Regex

Theo Galanakis <Theo(dot)Galanakis(at)lonelyplanet(dot)com(dot)au> writes:
> Basically the regex should return TABLEA, TABLEB from:

> Select *
> from TABLEA
> Inner jon TABLEB on tableb.columna = tablea.columna

You realize of course that this problem is mathematically impossible?
Regexes are less powerful than context-free grammars, and so it is a
certainty that there exist legal SQL statements that will fool any regex
that you invent for this purpose.

If you know that the SQL statements are coming from a query generator
that produces only a certain style of SQL code, then you might be able
to come up with a solution that works reliably for the output of that
query generator. But I wonder if you wouldn't be better off bypassing
the parse-and-deparse hacking and tapping directly into the query
generator.

regards, tom lane