I am attempting to write a query that returns the the number of employees, the average salary, and the number of employees paid below the average. The query I have so far is: select trunc(avg(salary)) "Average Pay", count(salary) "Total Employees", ( select count(salary) from employees where salary < (select avg(salary) from employees) ) UnderPaid from employees; But when I run this I get the ora-00937 error in the subquery. I had thought that maybe the "count" function is what is causing the issue, but even running a simpler sub query such as: select trunc(avg(salary)) "Average Pay", count(salary) "Total Employees", ( select avg(salary) from employees ) UnderPaid from employees; still returns the same error. As both AVG and COUNT seem to be aggregate functions, I'm not sure why I'm getting the error? Thanks