hackerrank sql solutions interviews sql hackerrank hard problem

certainly! hackerrank is a popular platform for coding challenges and interviews, particularly in sql. this tutorial will cover a hard sql problem commonly found on the platform, providing a structured approach to solving it, along with a code example.

problem overview: employee salary

**problem statement:**
you have a database table named `employee`, which has the following columns:
- `id`: an integer representing the employee's unique identifier.
- `name`: a string representing the employee's name.
- `salary`: an integer representing the employee's salary.

your task is to find the names of employees who earn more than the average salary in the company. the result should be sorted alphabetically by the employee's name.

sql table structure

sample data

solution approach

1. **calculate the average salary**: first, you need to find the average salary of all employees.
2. **filter employees**: use the average salary to filter out employees who earn more than this average.
3. **sort the results**: finally, sort the names of the qualifying employees in alphabetical order.

sql query

here’s how you can implement the solution in sql:

explanation of the query

1. **subquery**: `(select avg(salary) from employee)` calculates the average salary across all employees. this value is used to filter employees.
2. **main query**: the main `select` statement retrieves names from the `employee` table where the salary is greater than the computed average.
3. **ordering**: `order by name` sorts the results alphabetically.

additional notes

- **performance considerations**: when working with large datasets, consider the performance implications of subqueries. in some situations, using `join` or common table expressions (ctes) can be more efficient.
- **handling nulls**: make sure to handle cases where the salary might be null, which could affect the average calculation. however, in this specific problem setup, we assume all salaries are valid integers.

testing th ...

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