Index

An index is a special database object that lets you quickly locate particular records based on key column values. Indexes are essential for good database performance.

The index creation process requires a temporary segment if the data cannot be sorted in memory. Indexes can be created with the nologging option.

Creating indexes

Normal indexes:

CREATE INDEX emp_ind1 ON emp(deptno);

Normal composite indexes:

CREATE INDEX emp_ind1 ON emp(empto, deptno);

Bitmap index:

CREATE BITMAP INDEX emp_ind2 ON bigemp(sex);

Function-based indexes (query rewrite must be enabled):

CREATE INDEX emp_ind3 ON emp(deptno*1.1);

CREATE INDEX emp_ind3 ON emp(deptno DESC);

Also see

• Index-organized table

Glossary of Terms
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