Visual Explain Overview
You can use Visual Explain to create a query graph that graphically displays the execution
of your SQL statements. You can use this tool to see information about both
static and dynamic SQL statements. Visual Explain supports the following types of SQL statements:
- Select
- Insert
- Update
- Delete
You can also use this tool to better
understand where the highest costs of your queries are taking place. You
can improve query performance by:
- Rewriting your SQL statement.
- Changing query attributes and environment settings.
- Causing recommended indexes to be created.
You can also use Visual Explain to:
- View the statistics that were used at the time of
optimization.
- Determine whether or not an index was used to access
a table. If an index was not used, Visual Explain can help you determine
which columns might benefit from being indexed.
- View the effects of performing various tuning
techniques by comparing the before and after versions of the query graph.
- Obtain information about each operation in the query graph,
including the total estimated cost and number of rows retrieved.
- View the debug messages issued by the Query Optimizer during the query execution.
For more information, see Database Performance and Query Optimization in the
Information Center
.