"Never use SELECT * in code."

Along the lines of "never say never", I find this oft repeated bit of advice completely misleading. Certainly one can get in trouble with "SELECT *" and should know about its pitfalls. But there are many situations in which it is perfectly fine to use it and others in which it is the *only* thing to use.

Example 1: if you are using bind_columns (which is, after all, the fastest way to fetch), then this is fine: 

    my $sth = $dbh->prepare("SELECT * FROM foo");
    $sth->execute;
    my %row;
    $sth->bind_columns( \( @row{ @{$sth->{NAME_lc} } } ));
    while ($sth->fetch) {
        print "$row{region}: $row{sales}\n";
    }

[download]

Example 2: You want to display a table to examine it's structure visually, without knowing its structure in advance.

Should one be wary of code that expects the structure of a table to remain unchanged? Yep. Should one therefore never use "SELECT *"? Nope.

In reply to Re: Re: selecting again from a mysql database by jZed
in thread selecting again from a mysql database by bory

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.