$uid = 1;
$result = db_query('SELECT n.nid, n.title, n.created
FROM {node} n WHERE n.uid = :uid', array(':uid' => $uid));
Fetch next row as a stdClass object.
$record = $result->fetchObject();
Fetch next row as an associative array.
$record = $result->fetchAssoc();
Fetch data from specific column from next row.Defaults to first column if not specified as argument
$data = $result->fetchColumn(1);
Grabs the title from the next row. Retrieve all records into an indexed array of stdClass objects.
$result->fetchAll();
Retrieve all records as stdObjects into an associative array.keyed by the field in the result specified.(in this example, the title of the node)
$result->fetchAllAssoc('title');
Retrieve a 2-column result set as an associative array of field 1 => field 2.
$result->fetchAllKeyed();
Also good to note that you can specify which two fields to use by specifying the column numbers for each field
$result->fetchAllKeyed(0,2); // would be nid => created
$result->fetchAllKeyed(1,0); // would be title => nid
Retrieve a 1-column result set as one single array.
$result->fetchCol();
Column number can be specified otherwise defaults to first column
$result->fetchCol($db_column_number);
Count the number of rows
$result->rowCount();