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Monday, December 11, 2017

Difference between b-tree and bitmap index

A bitmap and a btree indexes are used to retrieve rows faster than a full-table scan.  

Below are the basic differences between b-tree and bitmap indexes :

1:  Syntax of bitmap and a B-tree indexes:  
  • The bitmap index includes the "bitmap" keyword.  
  • The btree index does not say "bitmap"

2: Cardinality differences:  
  • The bitmap index is generally for low cardinality columns (Columns with duplicate values )
  • while b-tree indexes are best for high cardinality columns.

3: Internal structure differences:  
  • A B-tree index has index nodes (based on data block size), it like a tree form

  • A bitmap index looks like this, a two-dimensional array with zero and one (bit) values

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