The SQL Query Rewrite Facility
in SPD Server examines SQL queries in order to optimize processing
performance. Some SQL queries contain SQL statements and sub-queries
that can be more rapidly evaluated in a separate space, as opposed
to sequentially evaluating large blocks of SQL statements. When SPD
Server detects and processes SQL statements or sub-queries in a separate
space, intermediate result tables are produced. The original SQL query
is dynamically rewritten, using intermediate results tables to replace
the SQL code that was evaluated separately. The result is a dynamic
process that evaluates and processes SQL queries more efficiently.
Inserting the derived
intermediate data into the original SQL query does not change the
quantitative results. Rather, the processing that is required to
calculate them is expedited. The SQL Query Rewrite Facility does not
change the content of the query's answer row set. However, the order
of the rows in the query answer set might vary if you compare the
optimized query answer set with the query answer set that SPD Server
generates with the SQL Query Rewrite Facility disabled.