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in reply to need to parse firts part of SQL-query (regex question)

To expand on roboticus's comments - there is a SQL::Tokenize (I think that's the name) module on CPAN which works pretty well at tokenizing a SQL query. You could use that as a starting point.

Michael

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Re^2: need to parse firts part of SQL-query (regex question)
by Not_a_Number (Prior) on Jan 17, 2008 at 17:05 UTC

    Do you mean SQL::Tokenizer? That doesn't seem to do what the OP wants:

    use SQL::Tokenizer;

my $query = q{f1,f2, SUM(f3),CONCAT(f4,f5, f6), f7};

my @tokens = SQL::Tokenizer->tokenize($query);
print join "\n", @tokens;

__END__
f1
,
f2
,

SUM
(
f3
)
,
CONCAT
(
f4
,
f5
,

f6
)
,

f7

    [download]
[reply]
[d/l]
      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)

      [download]

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

      • another intruder with the mooring in the heart of the Perl

[reply]
[d/l]

        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;

        [download]

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

[reply]
[d/l]
      Agreed - but this seems to me to be a good starting place.

      I used this to parse SQL source files for over a thousand stored procedures and check that the case of variables, columns, etc. matched when moving a system from a case-insensitive dataserver to a case-sensitive one. It required doing quite a bit of hand-coding to handle the various language elements of Transact-SQL, and ended up with about 700 lines of code to do all the checks, but I mostly got it done...

      Michael

[reply]
Re^2: need to parse firts part of SQL-query (regex question)
by roboticus (Chancellor) on Jan 17, 2008 at 16:32 UTC
[reply]

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