Beefy Boxes and Bandwidth Generously Provided by pair Networks
good chemistry is complicated,
and a little bit messy -LW
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
DBI 1.29 is out. There is a change in the specification. (And possibly a discrepancy in previous releases, read on.)
fetchrow_array in scalar context is not guaranteed to return the first column, as previously stated.

I am posting this warning because I have seen some SOPWs where people were using this particular idiom.

I quote from the release notes:
Changes in DBI 1.29, 15th July 2002

NOTE: This release changes the specified behaviour for the fetchrow_array method when called in a scalar context: The DBI spec used to say that it would return the FIRST field. Which field it returns (i.e., the first or the last) is now undefined. This does not affect statements that only select one column, which is usually the case when fetchrow_array is called in a scalar context.
FYI, this change was triggered by discovering that the fetchrow_array implementation in Driver.xst (used by most compiled drivers) didn't match the DBI specification. Rather than change the code to match, and risk breaking existing applications, I've changed the specification (that part was always of dubious value anyway).
Rather than using fetchrow_array in scalar context, consider calling it by assigning to a one-element list:
my $sth=$dbh->prepare("SELECT surname,name from people"); $sth->execute(); while (my ($surname) = $sth->fetchrow_array()) { # do something with $surname }
However, selecting two or more columns and then fetching only one is a plain waste of resources. If you need to fetch only the first column of a query, I recommend that you be specific and ask for that column only.

One more warning, from the same source. Future versions of the DBI may not support Perl 5.5 any longer. If you have database applications, consider upgrading to Perl 5.6.1.
 _  _ _  _  
(_|| | |(_|><
 _|   

In reply to DBI specification change by gmax

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!
  • 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, 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, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            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.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others avoiding work at the Monastery: (11)
    As of 2014-07-30 10:17 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      My favorite superfluous repetitious redundant duplicative phrase is:









      Results (230 votes), past polls