January 2012
Intermediate to advanced
542 pages
11h 28m
English
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Avoiding sorting in set operations: union, minus, and intersect
In this recipe, we will investigate performance-related issues when using set operations, such as UNION, INTERSECT, and MINUS.
Getting ready
We will use the SH schema and a copy of the EMPLOYEES table from the HR schema to do our test. To create the MY_EMPLOYEES table in the SH schema, we will use the following script:
CONNECT / AS SYSDBA CREATE TABLE sh.MY_EMPLOYEES AS SELECT * FROM hr.EMPLOYEES;
How to do it...
The following steps will demonstrate how to avoid sorting:
- Connect to the
SHschema and enable tracing:CONNECT sh@TESTDB/sh SET AUTOT TRACE EXP STAT
- Execute a query using the
UNIONoperator to show the customers with a credit limit higher than 13000 and the employees with a ...
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