second_highest_salary.sql

/*
Write an SQL query to report the second highest salary from the Employee table. If there is no second highest salary, the query should report null.
*/
WITH rank_table AS (
    SELECT
        salary,
        dense_rank() OVER (
            order by
                salary desc
        ) as rnk
    from
        employee
)
select
    case
        when max(rnk) = 1 then null
        else salary
    end as SecondHighestSalary
from
    rank_table
where
    rnk = 2;