Index-Organized Table


An Oracle index-organized Table is a table stored in an index B-Tree structure. There is no second data structure (heap-table) for the table. The Oracle database always uses the primary key as clustering key. An Index-Organized Table is created with the ORGANIZATION INDEX clause:

CREATE TABLE (
   id    NUMBER NOT NULL PRIMARY KEY,
   [...]
) ORGANIZATION INDEX

Accessing table data via a secondary index is slower than a similar query on a heap-table.

SQL Server supports index-organized tables as well, but uses the term clustered index.

About the Author

Photo of Markus Winand
Markus Winand tunes developers for high SQL performance. He also published the book SQL Performance Explained and offers in-house training as well as remote coaching at http://winand.at/