What is the difference between AND and OR in SQL?

What is the difference between AND and OR in SQL?

In SQL, AND and OR are logical operators used to filter records based on multiple conditions. AND requires all conditions to be true, while OR requires at least one condition to be true.

Can you give me an example of how to use both in a query?

Sure! For example, SELECT * FROM employees WHERE department = 'Sales' AND salary > 50000 retrieves employees in Sales with a salary over 50,000. Using OR, SELECT * FROM employees WHERE department = 'Sales' OR department = 'Marketing' retrieves employees in either Sales or Marketing.

What happens if I mix AND and OR in the same query?

When mixing AND and OR, SQL evaluates AND conditions first. You can use parentheses to control the order of evaluation. For example, SELECT * FROM employees WHERE (department = 'Sales' OR department = 'Marketing') AND salary > 50000 ensures the OR condition is evaluated first.

Are there any performance considerations when using these operators?

Yes, using AND can be more efficient if it reduces the result set significantly. However, complex queries with multiple OR conditions can lead to slower performance, especially if indexes are not used effectively.