[SQL문제풀기] Count Salary Categories

Can you solve this real interview question? Count Salary Categories - Table: Accounts +-------------+------+ | Column Name | Type | +-------------+------+ | account_id | int | | income | int | +-------------+------+ account_id is the primary key (column with unique values) for this table. Each row contains information about the monthly income for one bank account.   Write a solution to calculate the number of bank accounts for each salary category. The salary categories are: * "Low Salary": All the salaries strictly less than $20000. * "Average Salary": All the salaries in the inclusive range [$20000, $50000]. * "High Salary": All the salaries strictly greater than $50000. The result table must contain all three categories. If there are no accounts in a category, return 0. Return the result table in any order. The result format is in the following example.   Example 1: Input: Accounts table: +------------+--------+ | account_id | income | +------------+--------+ | 3 | 108939 | | 2 | 12747 | | 8 | 87709 | | 6 | 91796 | +------------+--------+ Output: +----------------+----------------+ | category | accounts_count | +----------------+----------------+ | Low Salary | 1 | | Average Salary | 0 | | High Salary | 3 | +----------------+----------------+ Explanation: Low Salary: Account 2. Average Salary: No accounts. High Salary: Accounts 3, 6, and 8.