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PERL - another quick hash of hashes question

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# 1  
Old 08-30-2009
PERL - another quick hash of hashes question

Hi, sorry, two hash related questions in one day .. but this has got me a bit stuck.

I have a mysql database table that kind of looks like this, the table is called "view1" and a snippet of that table (SELECT'ing just rows with serial number 0629AN1200) is below

   serial     nic_name      nic_ip   nic_duplex      nic_speed

0629AN1200 	bge0 	full     	10 
0629AN1200 	bge1 	full     	100 
0629AN1200 	bge2 	half    	100 	
0629AN1200 	bge3 	full 	        1000

i am creating a hash of hashes from this data ,using the code below

#!/usr/bin/perl -w
use DBI;

my $serial = "0629AN1200";   # an example serial number

my $dbh = DBI->connect("DBI:mysql:CMDB","username","password",) or die $DBI::errstr;
my $sth = $dbh->prepare("SELECT nic_name,nic_ip,nic_duplex,nic_speed FROM view1 WHERE serial = '$serial'") or die $DBI::errstr;
$sth->execute or die $DBI::errstr;
$hashr = $sth->fetchall_hashref('nic_name');

# I am using this bit of code to display the contents and structure of the hash of hashes

while ( my ( $key, $value ) = each %$hashr ) {
     print $key, " ->\n";
    while ( my ( $key, $value ) = each %$value ) {
        print "\t", $key, " -> ", $value, "\n";

when i run this script I get this output...note that even though I have asked fetchall_hashref to create keys based on 'nic_name', the output below still ALSO has 'nic_name' as a key value pair of the sub hash ..... ?

$ ./
bge3 ->
        nic_ip ->
        nic_speed -> 1000
        nic_name -> bge3
        nic_duplex -> full
bge1 ->
        nic_ip ->
        nic_speed -> 100
        nic_name -> bge1
        nic_duplex -> full
bge0 ->
        nic_ip ->
        nic_speed -> 10
        nic_name -> bge0
        nic_duplex -> full
bge2 ->
        nic_ip ->
        nic_speed -> 100
        nic_name -> bge2
        nic_duplex -> half

Is there something im doing wrong here ? I was under the impression that the line ...

$hashr = $sth->fetchall_hashref('nic_name');

would set the top level keys of the hash of hashes. .(which it seems to have successfuilly done) ... but would then have the intelligence to omit that particular key/value pair from the sub hash?

am i missing something here??

Any help would be great

Last edited by hcclnoodles; 08-30-2009 at 05:46 PM..
# 2  
Old 08-30-2009
Originally Posted by hcclnoodles
Is there something im doing wrong here ? I was under the impression that the line ...

$hashr = $sth->fetchall_hashref('nic_name');

would set the top level keys of the hash of hashes. .(which it seems to have successfuilly done) ... but would then have the intelligence to omit that particular key/value pair from the sub hash?
That is by design. Check the DBI documentation at

# 3  
Old 08-31-2009
thanks, its a bit of a pain considering im looping through all the key/value pairs in the sub hash. im going to have to code in an exception as technically its repeated information ...

thanks for clearing it up

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