[development] [Drupal7] Efficient to query nodes from multiple terms (CCK)
nan_wich at bellsouth.net
Sun Feb 27 19:19:22 UTC 2011
An important thing to remember is that what looks complex to you is not
necessarily complex to the database. Many people are scared to death of JOINs
because they think that makes the statement complex, while, in reality, they
often make the statement simpler to the database. Just make sure you (the
coder) know the difference between INNER and LEFT JOINs.
And some times, a subquery is the only way to get accurate results. For example,
getting a count of matching items from one table based on a selection from
another is generally going to give you erroneous (and much slower) results
without a subquery.
And I echo the "test more than one solution" sentiment. I usually will pop
over to PhpMyAdmin and test a query first to make sure it gives me what I
expect. There I can also break out subqueries (and JOINs) to see if they give me
what I expect. This is much better than the customer coming back and saying,
"Are you sure this screen is right?"
Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.
From: Pierre Rineau
The only suggestion I would give you is don't be afraid of complex SQL
queries, the only important thing is to always use direct (join|where|
etc) conditions over indexed fields.
Sometime subqueries can speedup a complex query, not always, test more
than one solution using EXPLAIN
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