Databases Reference
In-Depth Information
Summary
Indexes exist primarily to increase query performance, so it's critical that you think carefully about how
to implement indexes. A well planned indexing strategy results in a well performing database
application. Conversely, a careless plan will result in poor performance.
Indexes consume space on disk and are stored separately from tables. However, indexes are defined
on a table and one or more columns; in this sense, an index can't exist without the table.
Oracle provides a wide number of indexing types and features. In most situations, the default B-tree
index is appropriate. Before using other index types, make sure you understand the performance
benefits. You should be aware of the indexing features that Oracle provides and under what
circumstances you should employ specialized index types.
We recommend that you place indexes on primary key, unique key, and foreign key columns. This is
a good starting point. Furthermore, analyze slowly performing SQL statements to see which columns are
used. This will provide you additional candidate columns for indexing. These indexing
recommendations lay the foundation for maximizing SQL query performance.
