Query preprocessing prepares the query for optimization. It may change the representation of a statement so that the SQL statement that SAP Sybase IQ generates for passing to a remote server is syntactically different from the original statement, even though it is semantically equivalent.
Preprocessing performs view expansion so that a query can operate on tables referenced by the view. Expressions may be reordered and subqueries may be transformed to improve processing efficiency. For example, some subqueries may be converted into joins.