This is a problem I have come across several times, in fact often in the case of constructing HTML tables from a database.

First:

  SELECT
    group, somedata
  FROM
    table
  ORDER BY
    group, somedata

[download]

Next:

  my $lastgroup = undef;
  while ( my $row = $sth->fetchrow_arrayref() ) {
    if ( $lastgroup ne $row->[0] ) {
      print( $row->[0] . "\n" );
      $lastgroup = $row->[0];
    }
    print( "  " . $row->[1] . "\n" );
  }

[download]
Update: I think setting $lastgroup initially to undef may be dangerous.. potenially a warning could be generated about using an undefined value in a comparison using the ne operator. So here is an update to the above routine that I think is safer: 
  my $lastgroup = undef;
  while ( my $row = $sth->fetchrow_arrayref() ) {
    if ( ( !defined( $lastgroup ) ) || 
         ( $lastgroup ne $row->[0] ) )
    {
      print( $row->[0] . "\n" );
      $lastgroup = $row->[0];
    }
    print( "  " . $row->[1] . "\n" );
  }

[download]

In reply to Re: mysql sorting by monarch
in thread mysql sorting by sulfericacid

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