March 27, 2016

What is difference between btree indexes and bitmap indexes?

1)Btree index:when ever we are requesting data using btree indexes columns using where clause then oracle server searching for indexes in database,if btree indexes columns are available in database then oracle server automatically creates btree structure,through btree structure only oracle server retrieve data very fast from data base .

2)Bitmap index:when ever we are using bitmap index then oracle server automatically creates bitmap table,it is mostly used in data-ware house applications.bitmap index is high performance compare to btree index because bitmap index internally creates bitmap table.

3)By default indexes are btree indexes. When ever we are creating the primary key ,unique key constraints automatically btree indexes are created.

If you want to create bitmap index then explicitly you have to mention the bitmap keyword at the time of creation of index. Bitmap index mostly created on lo cardinality columns.the table having wide range values.