select customer_idfrom Customerswhere revenue>0and year=2021;

| 2072|[The Winner University](https://leetcode.com/problems/the-winner-university/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_2072.sql)|| Easy|

| 2026|[Low-Quality Problems](https://leetcode.com/problems/low-quality-problems/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_2026.sql)|| Easy|

| 1978|[Employees Whose Manager Left the Company](https://leetcode.com/problems/employees-whose-manager-left-the-company/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1978.sql)|| Easy|

| 1821|[Find Customers With Positive Revenue this Year](https://leetcode.com/problems/find-customers-with-positive-revenue-this-year/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1821.sql)|| Easy|

| 1809|[Ad-Free Sessions](https://leetcode.com/problems/ad-free-sessions/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1809.sql)|| Easy|

| 1795|[Rearrange Products Table](https://leetcode.com/problems/rearrange-products-table/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/database/_1795.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|