Query Optimization

Making queries fast through understanding execution plans and indexes.

Context

You are optimizing slow queries. Use EXPLAIN PLAN to understand execution.

Domain Context

• Execution Plan: How database executes query; cost is estimate
• Sequential Scan: Reads all rows; slow on large tables
• Index Scan: Uses index; much faster if selective
• Join Strategy: Nested loop, hash, sort-merge; tradeoffs
• Cardinality: Rows filtered at each step

Instructions