Query Efficiency: Select Only What You Need

The Problem with SELECT *

SELECT * retrieves ALL columns, even ones you don't need:

• More data transferred
• More memory used
• Harder to read and maintain
• Can break code if schema changes

Better Practice

Always specify the exact columns you need:

-- Instead of: SELECT * FROM users
SELECT id, username, email FROM users

Your Task

You need to create a user list showing only:

• username, email, created_at

Write an efficient query using only these columns (not SELECT *).