A unique question help!

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

Hi Monks!
I am getting data from this table, but my issue is that some duplicated information has been displayed, I can not prevent that on the sql query side of the code, I need to do it on the Perl side, here is the part of the code doing it,

$user_data = "
<table cellpadding=\"0\" cellspacing=\"0\">
<thead>
 <tr>
  <td colspan=\"4\">User List</td>
 </tr>
</thead>";

for (my $i = 0; $i < @$sql_data; $i++) {
my $user = $sql_data->[$i]{user};
my $link = "<a href=\"goto.pl?user=$user\">$user</a>";
my $first = $sql_data->[$i]{first};
my $last = $sql_data->[$i]{last};
my $phone = $sql_data->[$i]{phone};
my $mail = $sql_data->[$i]{mail};
                             
$user_data = "$user_data<tr><td><div>$show</div></td><td><div>$last, $
+first</div></td><td>$phone</td><td><div>$email</div></td></tr>";
}
$user_data = "$user_data</table>";
[download]

Right there a have to test $user_data for duplicated values, and only get the unique ones.
Any help?!
Thank you!

Comment on A unique question help! Download Code

Replies are listed 'Best First'.
Re: A unique question help! by kennethk (Abbot) on Oct 14, 2009 at 17:19 UTC
I'm unclear why you cannot use ~~UNIQUE~~ DISTINCT in your SQL query, but you can use a hash to check if you've seen a given data value already. You've not made it clear what you expect to be unique, but if you assume that "user" should only be displayed once, you might want something like: $user_data = " <table cellpadding=\"0\" cellspacing=\"0\"> <thead> <tr> <td colspan=\"4\">User List</td> </tr> </thead>"; my %seen; for (my $i = 0; $i < @$sql_data; $i++) { my $user = $sql_data->[$i]{user}; if ($seen{$user}) { # <-- added flow control next; } $seen{$user} = 1; my $link = "<a href=\"goto.pl?user=$user\">$user</a>"; my $first = $sql_data->[$i]{first}; my $last = $sql_data->[$i]{last}; my $phone = $sql_data->[$i]{phone}; my $mail = $sql_data->[$i]{mail}; $user_data = "$user_data<tr><td><div>$show</div></td><td><div>$las +t, $first</div></td><td>$phone</td><td><div>$email</div></td></tr>"; } $user_data = "$user_data</table>"; [download] If your condition is more complex, you can use a list of lists (perllol) to check uniqueness in a parallel fashion. Update: Changed UNIQUE to DISTINCT above. Not quite sure why I always forget that keyword. Thanks, roboticus.	[reply] [d/l]
Re^2: A unique question help! by Anonymous Monk on Oct 14, 2009 at 17:34 UTC
I have to correct this line: `$user_data = "$user_data<tr><td><div>$show</div></td><td><div>$last, $ +first</div></td><td>$phone</td><td><div>$email</div></td></tr>";` [download] with `$user_data = "$user_data<tr><td><div>$link</div></td><td><div>$last, $ +first</div></td><td>$phone</td><td><div>$email</div></td></tr>";` [download] I would like to test all the data in "$user_data" to be unique.	[reply] [d/l] [select]
Re^2: A unique question help! by Anonymous Monk on Oct 14, 2009 at 17:45 UTC
Interesting, can you explain this line: `$seen{$user} = 1;` [download] Thanks!	[reply] [d/l]
Re^3: A unique question help! by kennethk (Abbot) on Oct 14, 2009 at 17:54 UTC
`%seen` is a hash, and so `$seen{$user} = 1;` sets the key stored in `$user` in `%seen` to `1` (perldata). `1` is true in Perl, so the second time the same key is encountered, the test `if ($seen{$user}) {` will be true, and the code will execute `next`, skipping ahead in the for loop.	[reply] [d/l] [select]
Re^2: A unique question help! by Anonymous Monk on Oct 14, 2009 at 17:41 UTC
It worked, thanks a lot!	[reply]
Re: A unique question help! by mickep76 (Beadle) on Oct 15, 2009 at 11:37 UTC
Hi Just assign it to a hash and the hash will automagically remove all duplicates. Example: `@list = ('a', 'a', 'a', 'b', 'c', 'd'); foreach(@list) { $unique{$_}++ } foreach(sort keys %unique) { printf "$_ : %s\n", $unique{$_} }` [download] And if you also increase the value for each assignment to the hash you also get the number of duplicates.	[reply] [d/l]