Sql Programming Tutorials, Guides & Best Practices

• Select Type: Type of query (simple, primary, subquery, etc.).
• Table: The table accessed by the query.
• Type: Type of access (e.g., index, ALL, ref, const).
• Possible Keys: Indexes considered by the optimizer.
• Key: Index used for the query.
• Rows: Estimated number of rows examined.
• Extra: Additional information, such as whether a temporary table or file sort is used.

Use EXPLAIN to identify full table scans (type = ALL) and optimize them by adding appropriate indexes.

SELECT name, department FROM employees;

Use WHERE to reduce result size early: