Understanding BITMAP is so easy

1. Syntax

CREATE BITMAP INDEX index_name ON table

2. An simple example


TABLE test(id, name address){
(1,Rob,New York)
(2,Mary,Orlando)
(3,Jason,Chicago)
(4,Lisa,New York)
(5,Kim,New York)
(6,Philip,Washington)
(7,Frank,New York)
(8,Elizabeth,New York)
(9,Klaus,New York)
...
}

if you want to find the result under the condition of 【Where address = 'New York'】,however, many rows meet the condition and then you won't get the benefits from the general index for efficient query. Here, you can create BITMAP INDEX:

New York	Orlando	Chicago	Washington
1	0	0	0
0	1	0	0
0	0	1	0
1	0	0	0
1	0	0	0
0	0	0	1
1	0	0	0
1	0	0	0
1	0	0	0

In this case,  select * from TABLE where address = "New York"  will be quickly execute to find the resultset according to "1" and "0".