Query_Processing_and_Optimization_Presentation.pptx

Query

1. Query Processing and Optimization Understanding how SQL queries are interpreted, optimized, and executed efficiently

2. Introduction • Query processing involves interpreting and executing a SQL query. • Query optimization finds the best execution strategy with minimal cost (CPU, I/O, time).

3. Query Processing Steps 1. Parsing and Translation – SQL → Relational Algebra; syntax & semantic checking. 2. Optimization – Generate and evaluate multiple equivalent query plans. 3. Execution – Execute the selected optimal query plan.

4. Query Optimization Techniques • Heuristic Optimization: Apply transformation rules (push selections, combine joins). • Cost-Based Optimization: Select the plan with the lowest estimated cost. • Join Order Optimization: Rearrange join sequence for better performance. • Use of Indexes: Utilize available indexes for faster retrieval.

5. Example SQL Query: SELECT name FROM Employee WHERE dept = 'HR' AND salary > 50000; Optimized Plan: • Use index on 'dept'. • Apply selection before projection. • Reduce intermediate result size.

6. Benefits ✅ Faster Query Execution ✅ Reduced Resource Usage ✅ Improved Scalability and Performance