Pre-12.0 versions of Adaptive Server performed all join queries using nested-loop joins. Version 12.0 adds merge joins as a query execution method for equijoins. Merge joins can produce dramatic improvements in query execution times, especially for joins involving several very large tables. By default, merge joins are not enabled. They can be enabled server-wide or for an individual session.
For information on configuring merge joins, see enable sort-merge joins and JTC in Chapter 17, “Setting Configuration Parameters,” in the System Administration Guide. For information on merge joins and query processing, see Chapter 7, “Access Methods and Query Costing for Joins and Subqueries,” in the Performance and Tuning Guide.
