finhagen:

If you're doing a report of employees by supervisor, or similar, another way to handle the project is to make the database do some of the work for you. For example, you might be able to make a query give you the information sorted conveniently, and then add a control break. Perhaps something like:

our $lname;
my $sth = $dbh->prepare(<<EOSQL);
  SELECT   sup.fname, sup.lname, sup.title, sup.supervisor,
           emp.fname, emp.lname, emp.title, emp.supervisor
  FROM     employeedb sup
  JOIN     employeedb emp ON .....
  ORDER BY sup.fname, sup.lname, emp.fname, emp.lname
EOSQL
$sth->execute or die $sth->errstr;
my $previous_supervisor = '';
while (my $aref = $sth->fetchrow_arrayref) {
   my ($sup_fname, $sup_lname, $sup_title,
       $emp_fname, $emp_lname, $emp_title) = @$aref;

   # control-break: if a new supervisor is found, skip a few lines and
+ add a header
   my $current_supervisor = "$sup_fname $sup_lname";
   if ($current_supervisor ne $previous_supervisor) {
      $R += 3; $C = 0;
      $worksheet0->write($R, $C++, "SUPERVISOR: ", $format_HEADER);
      $worksheet0->write($R, $C++, $current_supervisor, $format_HEADER
+);
      $R++; $C=0;
      $worksheet0->write($R, $C++, "First Name", $format_COL_HEADER);
      $worksheet0->write($R, $C++, "Last Name",  $format_COL_HEADER);
      $worksheet0->write($R, $C++, "Title",      $format_COL_HEADER);
      $worksheet0->write($R, $C++, "Supervisor", $format_COL_HEADER);
   }

   # Add employee to sheet
   $R++; $C=0;
   $worksheet0->write($R, $C++, $emp_fname,      $format_NORMAL);
   $worksheet0->write($R, $C++, $emp_lname,      $format_NORMAL);
   $worksheet0->write($R, $C++, $emp_title,      $format_NORMAL);
   $worksheet0->write($R, $C++, $emp_supervisor, $format_NORMAL);
}

[download]

(Yes, I know this doesn't match your task exactly, it's just an example you might be able to adapt.)

Your example shows nearly duplicated code, which indicates that you might be able to restructure your code to use a subroutine:

sub process_employee {
    my ($worksheet0, $employee, $format, $col, $row) = @_;
    my $sth = $dbh->prepare("SELECT fname, lname, title, supervisor "
                           ."FROM employeedb WHERE eid = ?");
    $sth->execute($employee) or die $sth->errstr;
    my ($fname, $lname, $title, $supervisor);
    while (my $aref = $sth ->fetchrow_arrayref)    {
        ($fname, $lname, $title, $supervisor) = @$aref;
        $worksheet0->write($row++, $col, $fname, $format);
        $worksheet0->write($row++, $col, $lname, $format);
        $worksheet0->write($row++, $col, $title, $format);
        $worksheet0->write($row++, $col, $supervisor, $format);
    }
    return $supervisor
}

my $supervisor = process_employee($worksheet0, $employee1, $format_PRD
+middle, 19, 26);
if (defined $supervisor) {
    process_employee($worksheet0, $supervisor, $format_AMCtop, 23, 11)
+;
}

[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.

In reply to Re: mysql DBI Nested Queries by roboticus
in thread mysql DBI Nested Queries by finhagen

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