N-th Distinct Salary Lookup

Your analytics team stores compensation values in an Employee table:

• Employee(id, salary)

You are also given a one-row parameter table:

• salary_request(n)

Return the n-th highest distinct salary across all employees.

Important details:

• Salary duplicates count as one rank (distinct ranking).
• If n is non-positive or there are fewer than n distinct salaries, return null.
• Output must be exactly one row and one column named:
  • nthHighestSalary

Solve this in both:

• SQL (SQLite 3.27.2)
• Pandas

employee:
| id | salary |
|----|--------|
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |

salary_request:
| n |
|---|
| 2 |

[
  {"nthHighestSalary": 200}
]

employee:
| id | salary |
|----|--------|
| 1  | 100    |
| 2  | 100    |
| 3  | 80     |

salary_request:
| n |
|---|
| 1 |

[
  {"nthHighestSalary": 100}
]

employee:
| id | salary |
|----|--------|
| 1  | 500    |

salary_request:
| n |
|---|
| 3 |

[
  {"nthHighestSalary": null}
]