updating the notes

Author: chaithrakc

leetcode/notes.md

@@ -12,5 +12,19 @@ where (emp.departmentId, emp.salary) in (select departmentId, max(salary)
                                         from employee
                                         group by departmentId);
 ```
+
+Using common table expression and correlated sub-query
+
+```
+with dept_max_sal as( 
+    select departmentId, max(salary) as highest_sal 
+    from employee 
+    group by departmentId
+    )
+select d.name as Department, e.name as Employee, e.salary as Salary
+from employee e inner join department d on e.departmentId = d.id
+where e.salary = (select highest_sal from dept_max_sal c where e.departmentId = c.departmentId)
+```
+
 https://leetcode.com/problems/department-highest-salary/