select employee_id, department_id

from (select*,count(employee_id) over(partition by employee_id)as EmployeeCountfrom Employee) EP

where EmployeeCount=1

or primary_flag='Y';

|------|----------------|-----------------------------------------------------------------------------------------------------------------------|---------------|---------------|-------------

| 3198|[Find Cities in Each State](https://leetcode.com/problems/find-cities-in-each-state/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_3198.sql)|| Easy|

| 3172|[Second Day Verification](https://leetcode.com/problems/second-day-verification/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_3172.sql)|| Easy|

| 1789|[Primary Department for Each Employee](https://leetcode.com/problems/primary-department-for-each-employee/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1789.sql)|| Easy|

| 1757|[Recyclable and Low Fat Products](https://leetcode.com/problems/recyclable-and-low-fat-products/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1757.sql)|| Easy|

| 1741|[Find Total Time Spent by Each Employee](https://leetcode.com/problems/find-total-time-spent-by-each-employee/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1741.sql)|| Easy|

| 1729|[Find Followers Count](https://leetcode.com/problems/find-followers-count/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1729.sql)|| Easy|