Prepares a query string and returns the prepared statement.
This method caches prepared statements, reusing them when possible. It also prefixes tables names enclosed in curly-braces.
$query: The query string as SQL, with curly-braces surrounding the table names.
DatabaseStatementInterface A PDO prepared statement ready for its execute() method.
public function prepareQuery($query) {
$query = $this
->prefixTables($query);
// Call PDO::prepare.
return parent::prepare($query);
}