Perl fetch without execute error - at end of execution - mysql

Question

My current perl code is running through all of the rows of the database query and then throwing a
DBD::mysql::st fetchrow_hashref failed: fetch() without execute() at ./recieveTxn.cgi
line 168.
At the end. It almost is like there's something that's not telling the loop to stop at the end of the rows, but I have written it just as the others.
So for example: The query would pull up
shortcode1
shortcode2
shortcode3
then throw the error here
$sql = "
SELECT
aPI.folder AS aPIfolder,
aPI.rowNum AS aPIrowNum,
hasInput,
evalCode
FROM
aPersonalItems as aPI
LEFT JOIN
pItems_special_inputs as SI
ON
aPI.folder = SI.folder AND
aPI.rowNum = SI.rowNum
WHERE
hasInput=1 AND
aPI.folder='$FORM{'folder'}'
ORDER BY
aPI.rowNum
";
$sth = $dbh->prepare( $sql );
$sth->execute();
my ($shortcoderow, $row);
my $shortcodeSQL = "
SELECT
*
FROM
pItemsShortCodes
WHERE
folder='$FORM{'folder'}'
ORDER BY
rowNum
";
my $shortcodeSTH = $dbh->prepare( $shortcodeSQL );
$shortcodeSTH->execute();
while( my $ref = $sth->fetchrow_hashref() ) {
my $shortCode;
my $isblank = 1;
my $rowNum = $ref->{'aPIrowNum'};
while(my $shortcodeRef = $shortcodeSTH->fetchrow_hashref())
#&& $rowNum == $shortcodeRef->{'rowNum'}) #line 168 above
{
$shortCode=$shortcodeRef->{'shortcode'};
print $shortCode."\n";
}
$shortcodeSTH->finish();
}

Answer 1

The problem is that you are processing more than one row from $sth.
Your code fetches a row from $sth, and then your code loops through every row from $shortcodeSTH, until there are no more rows. Then your code calls the finish() method on $shortcodeSTH. (Which is the normative pattern, since you've already fetched all the rows.)
Then, your code starts through the outer loop a second time, fetching a second row from $sth. When your code attempts to start through the $shortcodeSTH loop a second time, you've already fetched all of the rows and closed the statement handle. There aren't any more rows to retrieve. (The error returned would be different if you hadn't issued the call to the finish() method; the error message would be something about fetching past the end of the cursor, or already fetched last row, or something to that effect.)