/*
Meta & Salesforce SQL Interview Question

Find the highest salary among salaries that appears only once.
*/

-- Schema Setup
CREATE TABLE employee(id INT,first_name VARCHAR(50),last_name VARCHAR(50),age INT,sex VARCHAR(1),employee_title VARCHAR(50),department VARCHAR(50),salary INT,target INT,bonus INT,email VARCHAR(100),city VARCHAR(50),address VARCHAR(100),manager_id INT);

INSERT INTO employee (id, first_name, last_name, age, sex, employee_title, department, salary, target, bonus, email, city, address, manager_id)VALUES(5, 'Max', 'George', 26, 'M', 'Sales', 'Sales', 1300, 200, 150, 'Max@company.com', 'California', '2638 Richards Avenue', 1),(13, 'Katty', 'Bond', 56, 'F', 'Manager', 'Management', 150000, 0, 300, 'Katty@company.com', 'Arizona', NULL, 1),(11, 'Richerd', 'Gear', 57, 'M', 'Manager', 'Management', 250000, 0, 300, 'Richerd@company.com', 'Alabama', NULL, 1),(10, 'Jennifer', 'Dion', 34, 'F', 'Sales', 'Sales', 1000, 200, 150, 'Jennifer@company.com', 'Alabama', NULL, 13),(19, 'George', 'Joe', 50, 'M', 'Manager', 'Management', 250000, 0, 300, 'George@company.com', 'Florida', '1003 Wyatt Street', 1),(18, 'Laila', 'Mark', 26, 'F', 'Sales', 'Sales', 1000, 200, 150, 'Laila@company.com', 'Florida', '3655 Spirit Drive', 11),(20, 'Sarrah', 'Bicky', 31, 'F', 'Senior Sales', 'Sales', 2000, 200, 150, 'Sarrah@company.com', 'Florida', '1176 Tyler Avenue', 19);

-- Solution
SELECT
   salary AS highest_unique_salary
FROM employee
GROUP BY salary
HAVING COUNT(salary) = 1
ORDER BY salary DESC
LIMIT 1;