3

CHAPTER 3

AND, OR, NOT

Combining multiple conditions into one filter.

5

Learning Blocks

SQL

Interactive Queries

In This Chapter

Concepts you'll master

AND: both conditions must be true

OR: at least one condition must be true

NOT: invert a condition

Parentheses to control evaluation order

SQL QUERY

SELECT name, department, salary 
FROM employees
WHERE department = 'IT' AND salary > 70000;

SQL QUERY

SELECT name, department 
FROM employees
WHERE department = 'IT' OR department = 'HR';

5.3 - NOT

Everyone except Salses

SQL QUERY

SELECT name, department 
FROM employees
WHERE NOT department = 'Sales';

5.4 - Parentheses - Always Be Explicit

❌ Common Mistake: AND has higher precedence than OR, just like multiplication vs addition in maths. WHERE a OR b AND c is evaluated as WHERE a OR (b AND c), which is almost never what you intended. Always use parentheses

SQL QUERY

SELECT name, department, salary 
FROM employees
WHERE department = 'Sales'
      OR (department = 'IT' AND salary > 80000);

Exercise

Practice your SQL skills

SQL EDITOR

Interactive Query Environment

Press semicolon (;) to auto-run query

Tasks

Complete all SQL challenges

Find employees who are in IT and have salary greater than 70000.

Current Task

Find employees who are in HR or Sales.

Find employees who have salary less than 60000 or work in IT.

Find employees who are not in Sales department.

Find employees who do have a manager (i.e., manager_id is NOT NULL)

Find employees who: are in IT or HR, and salary greater than 60000, and not in Sales

Need help solving this task?