Question on how cardinality is calculated.
- From: "Ronnie Doggart" <ronnie_doggart@xxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 10 Jan 2008 15:06:05 -0000
All
Does anyone know how Oracle calculates the cardinality of a query such
as:
Select * from table_1 where upper(case) like '%12345%';
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=131 Card=5553
Bytes=621936)
1 0 TABLE ACCESS (FULL) OF 'TABLE_1' (Cost=131 Card=5553
Bytes=621936)
Oracle calculates that it is expecting 5553 rows from this query but I
know it will only return 2.
How does it do its estimate ?
Ronnie Doggart
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