Drupal 7 Module Development

Database Access
Summary
Although in practice it's surprising how often we won't need to deal with the
database directly, we do in some way or the other. In this appendix we've seen how
to leverage Drupal's database layer to build powerful, cross-database queries that
are, in many cases, easier to work with than SQL, while still mirroring actual SQL.
• We've seen how to portably and securely write arbitrary SQL queries.
• We've seen how to allow other modules to modify our queries before
they're run.
• We've seen how to write complex queries that change based on user input
in a portable way.
• We now know how to write data modification queries that will be
automatically optimized for whatever database we happen to be using.
• We've seen how to use transactions to make our code more robust and
fault-tolerant.
• We understand how to support master/slave replication to allow sites
to scale to high levels of traffic.
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