Duplicity Check Help!

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

Hi Monks!
I am working on this code that allows users to upload pictures, to avoid page refreshes And not to have the SQL INSERT duplicating the record I am trying to check if the pictures is already in the database. I am kind of stuck here because of the value of “$flag_pic” been always set to one no matter what. I know I am missing something or it is just lack of sleep. As you can see I check if "@pics" is true first, the max numbers of pics in this array its only 4, but it can be 1 or 2 or 3 pics, its up to the user. As long as one of them are in the database I don’t want allow the insert to happen again. I hope I made my self clear.
Here is the part of the code (sample) I am having this issue:

...
if(@pics)
 {
  
    my $dbh = SQLStuff->connect_mysql();
    my $sth = $dbh->prepare("select * from test_users where user = ? "
+) or &justdie("Can't select from table: ",$dbh->errmsg); 
       $sth->execute($got_user_name);
       #my (@pic1,@pic2,@pic3,@pic4,$flag_pic);
       my $flag_pic;
       while (my $row = $sth->fetchrow_hashref()) 
        {
        #push @pic1,$row->{image_name_1} || '';
        #push @pic2,$row->{image_name_2} || '';
        #push @pic3,$row->{image_name_3} || '';
        #push @pic4,$row->{image_name_4} || '';
        if(($row->{image_name_1} ne "") eq ($pics[0] ne "")){$flag_pic
+="1";}
        if(($row->{image_name_2} ne "") eq ($pics[1] ne "")){$flag_pic
+="1";}
        if(($row->{image_name_3} ne "") eq ($pics[2] ne "")){$flag_pic
+="1";}
        if(($row->{image_name_4} ne "") eq ($pics[3] ne "")){$flag_pic
+="1";}

         }

            #my $check_pic1 = shift(@pic1);
            #my $check_pic2 = shift(@pic2);
            #my $check_pic3 = shift(@pic3);
            #my $check_pic4 = shift(@pic4);
             print "<br>751**$flag_pic**<br>";
    # End check
    if($flag_pic ne "1")
     {
       my $dbh = SQLStuff->connect_mysql();
       my $sth = $dbh->prepare("insert into test_add(image_1,image_2,i
+mage_3,image_4,image_loc,user) values(?, ?, ?, ?, ?,?)") 
        or &justdie("Can't add data, please try again later! ",$dbh->e
+rrmsg); 
       $sth->execute((@pics, undef, undef, undef, undef)[0..3],$path_l
+oc[0],$got_user) or &justdie("Can't select from table: ",$dbh->errmsg
+);

     } 

 }
...
[download]

Thanks for looking!

Comment on Duplicity Check Help! Download Code

Replies are listed 'Best First'.
Re: Duplicity Check Help! by sundialsvc4 (Abbot) on Dec 02, 2010 at 14:37 UTC
`undef` is not-equal to “an empty string.” Therefore, each of your `if` statements evalues to true, and the variable gets incremented several times. Use the `defined()` function to check for a `NULL` field value, which comes across as `undef`. Be sure not to use an “empty string” value in a text column, unless “an empty string” is a plausible, non-`NULL` possibility in your application. (Unlikely.) As for myself, I am not a fan of using the `\|\| alternate_value` syntax. Although you might think of it as being a check for `NULL`, it is in fact a check for anything that evaluates to a `false` value according to whatever rules Perl may have. Which is why you see stuff like this in my code: `do { $$rec{$_} = "foo" unless defined($$rec{$_}) } foreach qw(FIELD1 FIELD2 FIELD3);` [download] There are many ways to write it, of course, but the idea is clear: for an arbitrarily-long list of field names, if any of the returned values is `undef` a specific value is substituted for them. (Since this is, of course, being applied against the in-memory (not `tie`d) hash returned by `DBI::fetchrow_hashref`, it does not modify the database in any way.) This uses the `foreach` modifier exactly as described in `perldoc perlsyn`.	[reply] [d/l]
Re^2: Duplicity Check Help! by Anonymous Monk on Dec 02, 2010 at 14:57 UTC
How would you apply your way to this code to do these checks?	[reply]
Re: Duplicity Check Help! by wallisds (Beadle) on Dec 02, 2010 at 15:27 UTC
I would be interested to see the description of your table 'test_add'. But in the meantime here are some of my initial suggestions: `my $flag_pic;` I would define it and turn on warnings (if not already on): `use warnings;` And for the defining part change `my $flag_pic;` to `my $flag_pic = 0;` [download] Also, where you say : `$flag_pic+="1";` [download] I think you should take away the quotes and try this please: `$flag_pic+=1;` [download] Now if I understand your question correctly you don't want to add any duplicate images into your table and you are checking this based on the value of $flag_pic. I notice you are saying `if ($flag_pic ne "1") { #insert }` but you are adding 1 up to 4 times (given the if statements succeed) in your while loop (as shown here so you know what I'm trying to say) `if ( ($row->{image_name_1} ne "") eq ($pics[0] ne "") ) { $flag_pic += "1"; } if ( ($row->{image_name_2} ne "") eq ($pics[1] ne "") ) { $flag_pic += "1"; } #and all the way to image_name_4` [download] ... so if you have two cases where the if succeeds, $flag_pic will be set to 2, not 1, and if you have three, $flag_pic = 3, and so forth. So in any case where more than one if-statement succeeds in your while loop $flag_pic will NOT EQUAL 1. I recommend changing your if-statement at the bottom to `if ($flag_pic == 0) { #insert }` See if any of that helps. -Dawn	[reply] [d/l] [select]
Re^2: Duplicity Check Help! by Anonymous Monk on Dec 02, 2010 at 16:08 UTC
Well, yes, I am trying to see if any of the images are already in the database, and if I find any match I am setting the value of "$flag_pic" to something, that way I know that a match was found and I don't have to run the INSERT part.	[reply]
Re^3: Duplicity Check Help! by wallisds (Beadle) on Dec 02, 2010 at 16:21 UTC
Right but what I'm trying to say is your insert code will run anytime $flag_pic is NOT EQUAL to '1' and in your while loop you are incrementing $flag_pic by 1 anytime the image name and pic exist. This is done four times in the while loop, which is fine, except in your IF (for inserting) you are saying if (flag_pic ne '1'). You need to check if ($flag_pic == 0) because $flag_pic is not equal to 1 if it equals 0 (which is what you are looking for) but it's also not equal to 1 if it equals 2,3 or 4 ... etc. Does that make sense? Try updating the code and see if it helps please.	[reply]
Re^4: Duplicity Check Help! by wallisds (Beadle) on Dec 02, 2010 at 17:05 UTC
Re^4: Duplicity Check Help! by Anonymous Monk on Dec 02, 2010 at 16:47 UTC
Re^5: Duplicity Check Help! by wallisds (Beadle) on Dec 02, 2010 at 17:26 UTC


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