Soooooo....Many thanks to Kyle and others for sticking with this even when I got crabby yesterday.

Really the central problem was extending a one-dimensional hash to a two-dimensional one and then expecting the first-dimension's keys to remain scalars. Having extended the original hash into a hash of hashes, clearly the first-dimension's keys had to become hash-refs.

With all due respect to Kyle, I don't believe it has anything at all to do with using "1".

The booklist_1 hash populating loop 

while ($book_id = $sth->fetchrow_array()) {
    $booklist_1{$book_id} = 1;
}

[download]
works just fine. There'd be something seriously fubar if you couldn't set the value of a variable to 1. At this point, keys %booklist_1 gives me the list of book_id's.

Where it gets messed up is in the second loop where I extend the hash 

$sql = "select update_id, title from booklist_table where (book_id = ?
+) order by update_id desc limit 1";
$sth = $dbh->prepare($sql) or die("Could not prepare!" . $dbh->errstr)
+;

foreach $book_id (keys %booklist_1) {

    $sth->execute($book_id) or die("Could not execute!" . $dbh->errstr
+);
    ($update_id, $title) = $sth->fetchrow_array();
    $booklist_1{$book_id}{'update_id'} = $update_id;
    $booklist_1{$book_id}{'title'} = $title;

    print "$book_id > $booklist_1{$book_id}{'update_id'}\n";
}
$sth->finish;

[download]
When I extend it to two dimensions, it becomes a hash of hashes and the first dimension's keys must become references to the second dimenion hashes. So now keys %booklist_1 is a bunch of hash references, and no longer the bunch of book_ids I set them to originally. Kyle set me onto this when he wrote

You can't have a $b{foo}{bar} and have $b{foo} set to some unrelated value (such as 1). If there is a $b{foo}{bar}, then $b{foo} must somehow be a reference to a hash where you access ->{bar}.

My final solution is to use distinct hashes, like this: 

$sql = "SELECT book_id FROM booklist_table WHERE (expected_publcn_date
+ >= '".$start_date."' AND expected_publcn_date <= '".$end_date."')";
$sth = $dbh->prepare($sql) or die("Could not prepare!" . $dbh->errstr)
+;
$sth->execute() or die("Could not execute!" . $dbh->errstr);
while ($book_id = $sth->fetchrow_array()) {
    $booklist_1_temp{$book_id} = 1;
}
$sth->finish;

$sql = "select update_id, title from booklist_table where (book_id = ?
+) order by update_id desc limit 1";
$sth = $dbh->prepare($sql) or die("Could not prepare!" . $dbh->errstr)
+;

foreach $book_id (keys %booklist_1_temp) {

    $sth->execute($book_id) or die("Could not execute!" . $dbh->errstr
+);
    ($update_id, $title) = $sth->fetchrow_array();
    $booklist_1{$book_id}{'update_id'} = $update_id;
    $booklist_1{$book_id}{'title'} = $title;

    print "$book_id > $booklist_1{$book_id}{'update_id'}\n";
}
$sth->finish;

[download]
Note the "_temp" added to the booklist_1 hash name in the first loop. Which works like a charm.




Time flies like an arrow. Fruit flies like a banana.

In reply to Re: Why is my code assigning the last-retrieved value to all elements in my hash? by punch_card_don
in thread Why is my code assigning the last-retrieved value to all elements in my hash? by punch_card_don

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