Hash of Array Comparision...

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi all, Iam trying to compare two "hash of arrays". The idea is to compare the values, subtract and Input into Database. The following pseudocode is what i thought up. Is this approach correct?
#####Pseudo Code begins...

<br>
$datainput=DBI->connect<br>("DBI:mysql:database=DATA;host=localhost...
+...)<br>
foreach ($hash1($key1))<br>
    {<br>
    foreach ($hash2($key2))<br>
        {<br>
        if $hash1($key1)==$hash2($key2)<br>
            {<br>
        $data1=$hash2($value1)-$hash1($key2);<br>
        $data2=$hash2 ($value2)-$hash2(key2);<br>
$datainput->do("INSERT INTO DATA VALUES($data1, $data2)<br>
            }<br>
        }<br>
    }<br>
$datainput->disconnect();<br>
exit;<br>
[download]

#####Pseudo Code ends...
Rgds,

Comment on Hash of Array Comparision... Download Code

Replies are listed 'Best First'.
Re: Hash of Array Comparision... by chromatic (Archbishop) on Dec 01, 2001 at 12:08 UTC
Nothing obviously wrong jumps out at me, though I'm not sure why you switch from $key1 and $key2 to $value1 and $value2. There's probably an easier way to do it without looping through all of the keys multiple times. Even if you do minimize the looping, there will be a performance penalty for your do() call within the loop. Better to prepare a statement with placeholders outside and execute it repeatedly. `my $dbh = DBI->connect("DBI:mysql:database=DATA;..."); my $sth = $dbh->prepare("INSERT INTO DATA VALUES(?, ?)"); foreach my $key (keys %hash1) { # check other hash $sth->execute($data1, $data2); }` [download]	[reply] [d/l]
Re: Hash of Array Comparision... by jlongino (Parson) on Dec 01, 2001 at 12:27 UTC
I don't think it will work the way you have this set up. I'm ignoring the database component but imagine you'll want to do something more like this: `use strict; my %hash1 = (1=>[5,4,3,2,1], 2=>[1,2,3], 3=>[8,9]); my %hash2 = (1=>[6,5,4,3,2], 3=>[4,5]); foreach my $key1 (keys %hash1) { if (exists $hash2{$key1}) { foreach my $ss (0..@{$hash1{$key1}}) { ## do subtraction here using $ss as subscripts: ## my $data1 = $hash1{$key1}[$ss] - $hash2{$key1}[$ss]; ## it's not clear from your code why you're subtracting ## keys from values. } } }` [download] HTH. --Jim	[reply] [d/l]