Thursday, February 28, 2008

SQL Execution Plan

Optimizer creates the execution plan as per statistics available on database objects

Different types of internal joins

  • nested loop joins (Both Small tables & Optimizer mode: First Rows)
  • hash joins (Big Tables, Join type: Equality, Optimizer mode: All Rows)
  • sort merge join (Big Tables, Join type: Inequality, Optimizer mode: All Rows)
  • star transformation joins

The statements with the maximum level will be first executed and returned for the next level statement to work on it.

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