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 separately evaluated. 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; it only expedites the processing
that is required to calculate them. 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 SPD Server
generates with the SQL Query Rewrite facility disabled.