Oracle PL/SQL: INDEXES: Bitmap Indexes - In most cases bitmap indexes are considered to be most appropriate for columns having low distinct v

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Snippet Name: INDEXES: Bitmap Indexes

Description: In most cases bitmap indexes are considered to be most appropriate for columns having low distinct valuesâ€”such as GENDER, MARITAL_STATUS, and RELATION. This assumption is not completely accurate, however. In reality, a bitmap index is always preferable for systems where the data is not frequently updated by multiple concurrent systems.

The advantages of bitmap indexes are that they have a highly compressed structure, making them fast to read and their structure makes it possible for the system to combine multiple indexes together for fast access to the underlying table.

Also see:
» INDEXES: View table indexes
» INDEXES: Analyze Index
» INDEXES: Block Dump
» INDEXES: Rebuild Reverse
» INDEXES:
» INDEXES: ENABLE (function-based index)
» INDEXES: DISABLE (function-based index)
» INDEXES: Alter Index Parallel
» INDEXES: Alter Index Deallocate Unused
» INDEXES: Alter Index Allocate Extent
» INDEXES: Virtual / NoSegment
» INDEXES: Reverse Key Indexes
» INDEXES: Bitmap Join Indexes
» INDEXES: Unique indexes
» INDEXES: Parallel Index
» INDEXES: Compute Statistics
» INDEXES: SORT and NOSORT
» INDEXES: Function-Based Index
» INDEXES: DROP index
» INDEXES: Alter index
» INDEXES: Single Column Non-unique
» INDEXES: Index Usage Notes
» Compressed Indexes
» Create INDEX

Comment: (none)

Language: PL/SQL
Highlight Mode: PLSQL
Last Modified: March 10th, 2009

-- Table Index:
 
  CREATE [UNIQUE|BITMAP] INDEX [schema.]index_name
      ON [schema.]table_name [tbl_alias]
         (col [ASC | DESC]) index_clause index_attribs
 
-- Bitmap Join Index:
 
   CREATE [UNIQUE|BITMAP] INDEX [schema.]index_name
      ON [schema.]table_name [tbl_alias]
         (col_expression [ASC | DESC])
            FROM [schema.]table_name [tbl_alias]
               WHERE condition [index_clause] index_attribs
 
-- Cluster Index:
 
   CREATE [UNIQUE|BITMAP] INDEX [schema.]index_name
      ON CLUSTER [schema.]cluster_name index_attribs