How to Efficiently Find the Third or Nth Maximum Salary in a Database?

Finding the Third or Nth Maximum Salary from a Salary Table

In the realm of data analysis, it's often necessary to retrieve specific information from large datasets, including finding the maximum values. When it comes to databases, salary tables are an essential source of information for employees' compensation.

One common challenge is finding the third or nth maximum salary from a salary table efficiently. This task can be accomplished using several methods:

Row Numbering:

This method uses the ROW_NUMBER() function to assign each row a sequential number based on its salary value in descending order. The desired result can be obtained by selecting rows with the appropriate RowNum values.

Example:

SELECT Salary,EmpName
FROM
  (
   SELECT Salary,EmpName,ROW_NUMBER() OVER(ORDER BY Salary) As RowNum
   FROM EMPLOYEE
   ) As A
WHERE A.RowNum IN (2,3)

Subquery:

This method utilizes a subquery to count the number of distinct salary values greater than the target salary. By matching the count to (n-1), it returns the desired salary.

Example:

SELECT *
FROM Employee Emp1
WHERE (N-1) = (
               SELECT COUNT(DISTINCT(Emp2.Salary))
               FROM Employee Emp2
               WHERE Emp2.Salary > Emp1.Salary
               )

Top Keyword:

The TOP keyword allows you to retrieve a specified number of rows from a sorted table. By applying the TOP and ORDER BY keywords in conjunction, you can obtain the desired maximum salaries.

Example:

SELECT TOP 1 salary
FROM (
      SELECT DISTINCT TOP n salary
      FROM employee
      ORDER BY salary DESC
      ) a
ORDER BY salary

These methods provide efficient ways to find the third or nth maximum salary from a salary table. The choice of method depends on the specific database system and the desired level of optimization.

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