1. Query Optimization Phases of query processing
Heuristical Processing Strategies
Cost Estimation in DBMS
Chapter 23(21)

2. Phases of query processing
Fig. 23(21).1
Query decomposition
Analysis,Normalization,Semantic analysis, Simplification,Query resructuring
Query optimization
Code generation
Runtime query execution

3. Heuristical Processing Strategies for Query Optimization
Perform selection as early as possible
Combine Cartesian product with a subsequent selection operation
rearrange operations so that most restrictive selections are execued first
Perform project as early as possible
compute common expressions once(pipeline)
Implemented into Rule based system : Table 23(21).4 (Oracle)

4. Cost Estimation in DBMS
dominate cost in query is disk access
cost:estimation the disk access of a query
explain select * from main order by name;