ITPEC FE Morning October 2023 Question 27
ITPEC FE Morning October 2023 — Question 27 of 80
SQL Query Optimizer — determines the most efficient execution plan for a query.
The query optimizer is a DBMS component that evaluates multiple possible execution strategies and selects the one with the lowest estimated cost.
- •Decides which indexes to use
- •Chooses join order and join algorithm
- •Estimates row counts and I/O cost for each plan
Why not others:
- (b) Minimizing rows is the job of the query itself (WHERE, LIMIT), not the optimizer
- (c) Parsing and network transmission are handled by separate components (parser, network layer)
- (d) Caching query results is done by a query cache, a distinct mechanism
Key rule: The optimizer picks how to execute, not what to execute — it never changes the query's logical result.
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