|584|[Find Customer Referee](https://leetcode.com/problems/find-customer-referee/)|[Solution](../master/database/_584.java)||| Easy|

|580|[Count Student Number in Departments](https://leetcode.com/problems/count-student-number-in-departments/)|[Solution](../master/database/_580.sql) | || Medium | Left Join

|577|[Employee Bonus](https://leetcode.com/problems/employee-bonus/)|[Solution](../master/database/_577.sql)||| Easy|

|197|[Rising Temperature](https://leetcode.com/problems/rising-temperature/)|[Solution](../master/database/RisingTemperature.sql)| O(n^2)|O(n)| Easy|

|197|[Rising Temperature](https://leetcode.com/problems/rising-temperature/)|[Solution](../master/database/_197.sql)| O(n^2)|O(n)| Easy|

|196|[Delete Duplicate Emails](https://leetcode.com/problems/delete-duplicate-emails/)|[Solution](../master/database/_196.sql)| O(n^2)|O(n)| Easy|

|184|[Department Highest Salary](https://leetcode.com/problems/department-highest-salary)|[Solution](../master/database/_184.sql)| O(n^2)|O(n)| Medium|

|183|[Customers Who Never Order](https://leetcode.com/problems/customers-who-never-order/)|[Solution](../master/database/_183.sql)| O(n^2)|O(n)| Easy|