SQL Query Optimization

What is SQL Query Optimization? 

 Query Optimization involves rewriting SQL queries to run faster and use fewer resources. 

 Key Benefits: 

 ⏱ Faster Execution 

 🔄 Reduced Resource Usage Improved Scalability

 📈 Use Indexes Wisely Use indexes on frequently searched or filtered columns. Avoid over-indexing, as it can slow down write operations. 

Example:

Minimize SELECT * Usage Fetching unnecessary columns wastes resources. Instead, specify only the required columns. 

Pro Tip: This reduces memory usage and improves query speed.

Use WHERE Instead of HAVING Use WHERE to filter rows before aggregation.

Reserve HAVING for filtering aggregated results. 

 

 Pro Tip: Filtering early reduces the dataset size and improves performance. 

Leverage Joins Effectively Use INNER JOIN for specific matching rows. 

 Avoid CROSS JOIN unless needed. Index join columns for faster lookups.

Pro Tip: Always use ON conditions in joins to avoid Cartesian products. Avoid Subqueries When Possible Subqueries can slow down queries; use joins when possible for better performance.

Example: Bad: Good: Limit Results with Pagination Fetching millions of rows is resource intensive. Instead, paginate results using LIMIT and OFFSET.

Pro Tip: Always fetch data in manageable chunks. Analyse Query Performance Execution plans show how the database executes your query. Identify slow parts of your query. Adjust indexing, joins, or filters based on insights.

Pro Tip: Tools like MySQL Workbench or SQL Server Management Studio make analysing plans easier.

Key Takeaways Optimize Your Queries

Use indexes strategically. Avoid fetching unnecessary data.

Analyse performance using execution plans. Write clean, structured queries.