SQL Leetcode: 177. Nth Highest Salary

177. Nth Highest Salary

Medium

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Write a SQL query to get the nth highest salary from the Employee table.

+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |
+----+--------+

For example, given the above Employee table, the nth highest salary where n = 2 is 200. If there is no nth highest salary, then the query should return null.

+------------------------+
| getNthHighestSalary(2) |
+------------------------+
| 200                    |
+------------------------+

1. Using Correlated Subquery

CREATE FUNCTION getNthHighestSalary(N INT)

RETURNS INT
BEGIN
RETURN (
SELECT
Salary as getNthHighestSalary
from Employee e1
where N-1 = (Select COUNT(DISTINCT salary) from employee e2
WHERE e2.salary > e1.salary)
UNION
Select null
limit 1

);
END

2. Using DENSE_RANK()

CREATE FUNCTION getNthHighestSalary(N INT)

RETURNS INT
BEGIN
RETURN (
WITH CTE AS (
SELECT
Salary,
DENSE_RANK() OVER (ORDER BY SALARY DESC) as rank_salary
from Employee
)
SELECT distinct SALARY AS getNthHighestSalary
FROM CTE
WHERE rank_salary = N

UNION
Select null
limit 1

);
END