Re^3: need to parse firts part of SQL-query (regex question)

[grinder]

That doesn't seem to do what the OP wants

Come now young man, where's your sense of adventure? With a bit of lookahead and a state machine you can easily massage the token stream into something useful:

use SQL::Tokenizer;

my $query = q{f1,f2, SUM(f3),CONCAT(f4,f5, f6), sum((f1+f2)*f3)};
my @token = SQL::Tokenizer->tokenize($query);

my $paren_depth = 0;
my $cache       = '';

while(my $val = shift @token) {
    if ($token[0] eq '(') {
        $paren_depth++;
    }
    if ($val eq ')') {
        $paren_depth--;
        if ($paren_depth == 0) {
            print $cache;
            $cache = '';
        }
    }
    if ($paren_depth) {
        $cache .= $val;
    }
    else {
        print "$val\n";
    }
}
__PRODUCES__
f1
,
f2
,
SUM(f3)
,
CONCAT(f4,f5, f6)
,
sum((f1+f2)*f3)

That's not too shabby. The tokenizer does the heavy lifting, you just have to put the pieces back together again.

[Not_a_Number]

grinder++ !

It's rather like a solution I came up with, albeit without using the module in question:

my $str = 'f1,f2, SUM(f3),CONCAT(f4,f5, f6), f7';

my ( $tok, @toks, $parens );

while ( $str ) {
  my $char = substr $str, 0, 1, '';
  
  $char eq ' ' and next;
  $char eq '(' and $parens++;
  $char eq ')' and $parens--; 
  $char eq ',' && ! $parens
               and push( @toks, $tok ), $tok = '', next;
  
  $tok .= $char;
  push @toks, $tok if ! $str;    
}

print join ' -- ', @toks;

...but I didn't want to post it for fear that it wouldn't be very robust. :)

[grinder]

fear that it wouldn't be very robust

Yes indeed. Real-world SQL is likely to have named the columns, so you have to deal with concat(f4, f5, f6) as "foobarquux (combined)". Before you know it, you have reimplemented SQL::Tokenizer!