Query Processing and Optimization

Query Processing and Optimization : Outline
Operator Evaluation Strategies
  • Query processing in general
  • „Selection
  • Join
Query Optimization
„
  • Heuristic query optimization
„
  • Cost-based query optimization
Query Tuning
Query Processing + Optimization
Operator Evaluation Strategies
„
  • Selection
„
  • Join
Query Optimization
Query Tuning
Evaluation of SQL Statement
The query is evaluated in a different order.
„
  • The tables in the from clause are combined using Cartesian products.
„
  • The where predicate is then applied.
„
  • The resulting tuples are grouped according to the group by clause.
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  • The having predicate is applied to each group, possibly eliminating some groups.
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  • The aggregates are applied to each remaining group.
  • The select clause is performed last.

To know more about this topic see the given pdf :

Query Processing and Optimization – PDF

 

 

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