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(Ovid: Death to Select Star!) Re: MySQL DBI Help

by Ovid (Cardinal)
on Sep 22, 2001 at 21:51 UTC ( #114082=note: print w/ replies, xml ) Need Help??


in reply to MySQL DBI Help

On a note totally unrelated to your question, I couldn't help but notice your SQL:

SELECT * FROM emails

I do a lot of heavy database work and I've been bitten by this type of SQL many times. As a general rule, when trying to write maintainable code, it's a good idea to be very specific about what you will allow. For example, consider the following SQL statement:

SELECT userid, email, contest FROM emails

That SQL statement has a variety of benefits:

  1. It's immediately obvious to the maintenance programmer exactly what is being requested.
  2. It's more efficient than selecting a bunch of columns you don't need, if you have more columns in the table than you're actually using.
  3. If you do a $sth->fetchrow_arrayref, you don't have to worry about columns in the database being reordered.
  4. If someone renames a column, you will understand faster why your $ref->{'contest'} autovivified a hash entry and produced an undef value.
  5. If someone removes a column from the database, you get the same benefit as mentioned in the fourth point.

If you're just writing a small program, or use very simple logic as what you have above, these issues may be less likely to impact you. However, as you do more and more work with databases, getting in the habit of stating explicitly what you want will reap tremendous rewards.

Cheers,
Ovid

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The title of this node is a reference to Death to Dot Star!, for those who may be confused.

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