CSCE 310 / 608 Database Systems. Chapter 16: Query Compiler. Query Compiler. Parsing Logical Query Plan. Grouping and Aggregation. Since produces no duplicates: ( L (R)) = L (R) Get rid of useless attributes: L (R) = L ( M (R)) where M contains all attributes in L
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Chapter 16: Query Compiler
Logical Query Plan
where M contains all attributes in L
SELECT year, MAX(birthdate)
WHERE name = starName
GROUP BY year;
U D E F
A B C
Evaluating Logical Query Plan
Physical Query Plan
Here describe some simple heuristics.
All we really need is a scheme that properly
ranks competing plans.
If condition has the form C1 OR C2, use:
where f1 is fraction of R satisfying C1 and
f2 is fraction of R satisfying C2