PostgreSQL – MAX Function

MAX function is an aggregate function that allows you to get the maximum of values.

Example:

Consider the employee table as shown below:

id	first_name	last_name	department	salary
101	bryan	walker	sales	50,000
102	alex	carpenter	accounts	55,000
103	sam	white	sales	60,000
104	john	barry	sales	54,000
105	bill	wood	accounts	65,000
106	robert	hopkins	support	70,000
107	david	lee	support	72,000
108	jack	sears	support	65,000
109	tom	young	sales	55,000

You can get the maximum of all salaries as shown below:

SELECT MAX(salary) FROM employee;

sum
------
72,000

You can use MAX function along with the group by clause. Example: To return maximum of salaries per department, you can group by department as shown below:

SELECT department, MAX(salary) FROM employee GROUP BY department;

department  sum
----------  ---
sales       60,000
accounts    65,000
support     72,000

You can filter grouped results using HAVING clause. Example: Below query returns only the departments that are paying a maximum salary of more than 60,000.

SELECT department, MAX(salary) FROM employee GROUP BY department HAVING MAX(salary)>60000;

department  sum
----------  ---
accounts    65,000
support     72,000