Bitmap index

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A bitmap index is a type of index that uses a string of bits to quickly locate rows in a table. Bitmap indexes are normally used to index low cardinality columns in a warehouse environment.

[edit] History

Bitmap indexes was introduced in Oracle version 7.3.4.

[edit] Examples

Bitmap Index:

CREATE BITMAP INDEX emp_bitmap_idx ON big_emp(sex);

Bitmap Join Index:

CREATE BITMAP INDEX emp_dept_loc ON emp(dept.loc)
  FROM emp, dept
 WHERE emp.deptno = dept.deptno
 TABLESPACE index_ts1; 
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