Query Engine Overview

 

DB2® UDB for iSeries™ provides two query engines to process queries: the Classic Query Engine (CQE) and the SQL Query Engine (SQE).

The CQE processes queries originating from non-SQL interfaces: OPNQRYF, Query/400, and QQQQry API. SQL based interfaces, such as ODBC, JDBC, CLI, Query Manager, Net.Data®, RUNSQLSTM, and embedded or interactive SQL, run through the SQE. For ease of use, the routing decision for processing the query by either CQE or SQE is pervasive and under the control of the system. The requesting user or application program cannot control or influence this behavior. However, a better understanding of the engines and of the process that determines which path a query takes can lead you to a better understand of your query's performance.

Along with the new query engine, several more components were created and other existing components were updated. Additionally, new data access methods were created for SQE.

 

Parent topic:

Performance and query optimization

 

Related information


Embedded SQL programming
SQL programming
Query (QQQQRY) API
Open Query File (OPNQRYF) command
Run SQL Statements (RUNSQLSTM) command