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Oracle index types (Read 10101 times)
Gerrit-Jan Linker
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Oracle index types
15.06.11 at 08:18:02
 
Oracle index types
 
Oracle index types:
1. B tree or Normal
2. Bitmap
3. Function based
4. Domain
5. Ascending or descending
 
In the system view dba_indexes the index_type column can take the following distinct values:
NORMAL
BITMAP
IOT - TOP
DOMAIN
LOB
FUNCTION-BASED BITMAP
FUNCTION-BASED NORMAL
CLUSTER
 
Implicit or Explicit:
Indexes may also be classified as implicit or explicit. Explicit indexes are created using the create index command and implicit indexes are created by Oracle when you e.g. enable a unique constraint on a table.
 
Rules when using indexes:
  • Use as few columns as possible  
  • Only index integers if possible
  • Use variations on the simple B-tree index (reverse key, compression, and function-based)  
  • Null values are not indexed  
  • Index columns used as foreign key references
  • Don’t use bitmap indexes when using a lot of DML

 
Source:
http://www.dbasupport.com/oracle/ora10g/Ora_Perf_Tuning2.shtml
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« Last Edit: 15.06.11 at 10:05:09 by Gerrit-Jan Linker »  

Gerrit-Jan Linker
Linker IT Software
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