Oracle: Histograms
When to use histograms:1. When the columns are used frequently in where clauses.
2. it's hightly skewed data distribution.
Creating Histograms:
- execute DBMS_STATS.GATHER_TABLE_STATS
('scott','emp', METHOD_OPT => 'FOR COLUMNS SIZE 10 sal');
( create a 10 bucket histograms on sal column of emp table)
The default number of buckets is 75
posted by James Pei @ 4:05 PM
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