SQL/MX 2.x Query Guide (G06.24+, H06.03+)

HP NonStop SQL/MX Query Guide—523728-003
ix
About This Manual
This guide describes the use and formulation of queries, how to understand query
execution plans, and how to affect the performance of NonStop SQL/MX databases. It
also provides information about:
•
How to improve query performance
•
How the SQL/MX optimizer chooses a query execution plan
•
How you can influence the optimizer’s choice of a plan
Audience
This guide is intended for database administrators and application programmers who
use SQL/MX to query an SQL/MX database and who have a particular interest in
issues related to query performance. Readers are expected to be data processing
professionals who have familiarity with general issues related to the performance of
database management systems and who understand relational database theory and
terminology.
You should also be familiar with the operating system and one of the host
programming languages, such as C/C++ or COBOL.
Organization
Examples are shown in interactive form, such as that used by the SQL/MX
conversational interface (MXCI) and Visual Query Planner (VQP).
Section 1, Compiling and Executing a Query Introduces the SQL/MX compiler and
executor.
Section 2, Accessing SQL/MX Data
Provides information about access methods.
Section 3, Keeping Statistics Current
Provides information about updating statistics
and histogram statistics.
Section 4, Reviewing Query Execution
Plans
Describes how to read query execution
plans.
Section 5, Forcing Execution Plans
Describes how to force query execution
plans.
Section 6, Query Plan Caching
Describes how query plan caching works and
how to view query plan caching statistics.
Section 7, Operators and Operator Groups
Provides information about operators used in
query execution plans.
Section 8, Parallelism
Describes how SQL/MX performs parallelism.