SQL Query and performance tuning - Explain and Analyse commands
🛠️ Understanding SQL Query Performance with EXPLAIN and ANALYZE When it comes to SQL optimization, the first and most powerful step is understanding how your queries are actually executed . While SQL is declarative—you tell the database what you want—what happens under the hood is procedural and driven by a query execution plan . This blog post will walk you through how to use PostgreSQL’s EXPLAIN and ANALYZE tools to explore, diagnose, and improve query performance, including how WHERE clauses and indexes influence plans . 🔍 Meet EXPLAIN : Peek Into the Execution Plan Let’s start simple: EXPLAIN SELECT * FROM staff; Output: Seq Scan on staff ( cost = 0.00 . .24 .00 rows = 1000 width= 75 ) Seq Scan : A full table scan—every row is read. Cost : Estimated computation units. Not real time, but useful for comparing query complexity. Width : Amount of data (in bytes) returned per row. 🟢 For small tables , a Seq Scan is typically fast enough. 🔴 For la...