தமிழில் - Coding Series - SQL : Second Highest Salary | SQL Interview | Data Engineer Interview

Video 192: This is the 47th video in our series "Crack SQL Interview in 50 Questions," and in this exercise, we continue with the topic of "Advanced String Functions"

We are given a Employee table which has Employee id and salary. We are asked to write a solution to find the second highest salary from the Employee table. If there is no second highest salary, return null

In this video, we are discussing four different approaches to finding the second highest salary from the Employee table:

*** Approach 1: n00b format using Subquery ***
This approach uses nested subqueries to find the second highest salary. It repeatedly finds the maximum salary that is less than the previous maximum salary until the second highest salary is obtained.

*** Approach 2: Correlated subquery ***
In this approach, a correlated subquery is used to count the number of distinct salaries greater than or equal to each salary in the main query. The salary where this count equals 3 represents the second highest salary.

*** Approach 3: Windows function with subquery format ***
This approach utilizes a window function DENSE_RANK() to rank the salaries in descending order. The outer query then selects the salary corresponding to the rank of 2, which represents the second highest salary.

*** Approach 4: Windows function with CTE table ***
Here, a Common Table Expression (CTE) is used to calculate the dense rank of each salary. The main query then selects the maximum salary where the rank is equal to 2, indicating the second highest salary.

These approaches demonstrate different methods of achieving the same result, showcasing the versatility of SQL in solving such problems.

For a comprehensive understanding of these SQL methodologies and their application, please refer to this explanatory video.

code: https://github.com/jeganpillai/crack_sql_interview_in_50_questions/blob/main/seq01_47_second_highest_salary.sql

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