Tutorials Programming Tutorials, Guides & Best Practices

• WHERE clause: Index columns frequently used in WHERE conditions to speed up searches.
• JOIN clause: Index columns used in joins to improve join performance.
• ORDER BY clause: Index columns used in sorting to avoid sorting operations.

While indexes improve read performance, they can slow down write operations (INSERT, UPDATE, DELETE). Only create indexes on columns that benefit the most from indexing.

Result: John, Mary, Steve

The UNION operator combines results from two or more SELECT statements, removing duplicates. Use UNION ALL to include duplicates.