Snippet Name: INDEXES: Bitmap Indexes
Description: In most cases bitmap indexes are considered to be most appropriate for columns having low distinct values—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
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-- 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 |