When should I use subqueries in SQL?

When should I use subqueries in SQL?

Subqueries are useful when you need to perform an operation that requires data from multiple tables or when you want to filter results based on aggregated data.

Can you give me an example of a subquery?

Sure! For instance, if you want to find employees who earn more than the average salary, you could use a subquery to first calculate the average salary.

Are there any performance considerations with subqueries?

Yes, subqueries can sometimes be less efficient than joins, especially if they return a large number of rows. It's important to analyze your specific use case.

When is it better to use a join instead of a subquery?

Joins are generally better when you need to combine rows from two or more tables based on a related column, especially for performance.