Beefy Boxes and Bandwidth Generously Provided by pair Networks
Problems? Is your data what you think it is?
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

If you want to search for entities which contain a "Foo" part then you need to do:

SELECT entity_id FROM entities WHERE part1='Foo' OR part2='Foo' OR part3='Foo' ... OR part12='Foo';

Or perhaps slightly more concise:

SELECT entity_id FROM entities WHERE 'Foo' IN (part1, part2, part3, ..., part12);

I'd much prefer something like:

SELECT e.entity_id FROM entities e INNER JOIN entity_parts ep ON e.entity_id=ep.entity_id WHERE ep.part='Foo'

When you get to searching for different combinations of parts, the advantages of joining become even more apparent:

SELECT e.entity_id FROM entities e INNER JOIN entity_parts ep1 ON e.entity_id=ep1.entity_id INNER JOIN entity_parts ep2 ON e.entity_id=ep2.entity_id WHERE ep1.part='Foo' AND ep2.part IN ('Bar', 'Baz')

And in terms of the e-mail example, it's much easier to, say, enforce a UNIQUE constraint over a single column.

use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

In reply to Re^4: In base 1, the number after 0 is: by tobyink
in thread In base 1, the number after 0 is: by chacham

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
  • 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.
  • 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 scrutinizing the Monastery: (12)
    As of 2015-07-31 08:47 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









      Results (276 votes), past polls