So I was trying to understand how ON DUPLICATE KEY UPDATE works. I want to add entries to a database so I naturally want to check if there are duplicates. If there are no duplicates then I want to insert, but if there are duplicates then I want the id/primary key for that entry. I read in another thread you can invoke the LAST_INSERT_ID; however, that only returns value if it inserted an entry. 
sub insert_entry {
    my $table=$_[0];    #table
    my $col=$_[1];
    my $entry=$_[2];    #value
    
    my $insert=sprintf(qq(INSERT INTO %s(%s) VALUES(%s) ON DUPLICATE K
+EY UPDATE id=LAST_INSERT_ID(id)),
             $dbh->quote_identifier($table),
             $dbh->quote_identifier($col),
             $dbh->quote($entry));
    my $sth=$dbh->prepare($insert);
    $sth->execute();
    
    if ($sth->last_insert_id()){ #if new insertion
         return;
    }
    else {
         return $sth->last_insert_id(); #if duplicate return key
    }    
}

[download]

In reply to return primary key if duplicate entry exists? by diyaz

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.