Drupal 7 Module Development

Database Access
Finally we execute the query. execute() takes the information we have provided,
runs the query through alter hooks if necessary, compiles the corresponding SQL
string, and runs the query, returning a result object. The result object is the same as
that returned from a static query.
Also note that most methods of the select builder return the select object itself and
thus are chainable. The exceptions are the addField() and join() methods, as those
need to return a generated alias instead. The above query could therefore also have
been written as:
$query = db_select('node', 'n');
$u_alias = $query->innerJoin('users' ,'u', '%alias.uid = n.uid');
$query->addField($u_alias, 'name', 'username');
$result = $query
->fields('n', array('nid, title'));
->condition("{$u_alias}.name", 'Bob');
->condition('n.created', REQUEST_TIME - 604800, '>=');
->orderBy('n.created', 'DESC');
->range(0, 5);
->addTag('node_access')
->execute();
The query builder is capable of building far more complex queries, too, including
subselects, complex AND and OR conditions, among others. See the online
documentation for the full details.
Insert queries
While SELECT queries have both static and dynamic versions, INSERT, UPDATE,
DELETE, and MERGE queries only support a dynamic version. That is necessary in
order to support the full range of SQL databases in the wild, many of which require
extra special handling for some field types. As a nice bonus, the dynamic version of
these queries is often much easier to work with than the static version would be and
makes it easy to add additional database-specific optimizations. We'll look at Insert
queries first.
Just as with Select queries, Insert queries start with a constructor function and are
chainable. In fact, all methods of Insert queries are chainable.
$id = db_insert('imports')
->fields(array(
'name' => 'Groucho',
'address' => '123 Casablanca Ave.',
'phone' => '555-1212',
))
->execute();
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