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  • LeetCode——Nth Highest Salary

    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                    |
    +------------------------+
    

    此题相较于Second Highest Salary做了一些改进:

    • 创建mysql function;
    • 需要判断传入参数的合理性.

    因此,对代码改动如下所示:

    CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
    BEGIN
      DECLARE P INT DEFAULT N-1;
      IF (P<0) THEN
        RETURN NULL;
      ELSE
      RETURN (
          # Write your MySQL query statement below.
          SELECT IFNULL(
                (
                    SELECT DISTINCT Salary 
                    FROM Employee 
                    ORDER BY Salary DESC 
                    LIMIT P,1)
                ,NULL)
              AS SecondHighestSalary   
      );
      END IF;
    END
    

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  • 原文地址:https://www.cnblogs.com/jason1990/p/11639402.html
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