-- 2.1 Select the last name of all employees.
select LastName from Employees;
-- 2.2 Select the last name of all employees, without duplicates.
select distinct LastName from employees;
-- 2.3 Select all the data of employees whose last name is "Smith".
select * from employees where lastname = 'Smith';
-- 2.4 Select all the data of employees whose last name is "Smith" or "Doe".
select * from Employees where lastname in ('Smith', 'Doe');
select * from Employees where lastname = 'Smith' or lastname = 'Doe';
-- 2.5 Select all the data of employees that work in department 14.
select * from Employees where department = 14;
-- 2.6 Select all the data of employees that work in department 37 or department 77.
select * from employees where department = 37 or department = 77;
select * from employees where department in (37, 77);
-- 2.7 Select all the data of employees whose last name begins with an "S".
select * from employees where LastName like 'S%';
-- 2.8 Select the sum of all the departments' budgets.
select sum(budget) from Departments;
select Name, sum(Budget) from Departments group by Name;
-- 2.9 Select the number of employees in each department (you only need to show the department code and the number of employees).
SELECT Department, COUNT(*)
FROM Employees
GROUP BY Department;
-- 2.10 Select all the data of employees, including each employee's department's data.
select a.*, b.* from employees a join departments b on a.department = b.code;
SELECT SSN, E.Name AS Name_E, LastName, D.Name AS Name_D, Department, Code, Budget
FROM Employees E INNER JOIN Departments D
ON E.Department = D.Code;
-- 2.11 Select the name and last name of each employee, along with the name and budget of the employee's department.
/* Without labels */
SELECT Employees.Name, LastName, Departments.Name AS DepartmentsName, Budget
FROM Employees INNER JOIN Departments
ON Employees.Department = Departments.Code;
/* With labels */
SELECT E.Name, LastName, D.Name AS DepartmentsName, Budget
FROM Employees E INNER JOIN Departments D
ON E.Department = D.Code;
-- 2.12 Select the name and last name of employees working for departments with a budget greater than $60,000.
/* Without subquery */
SELECT Employees.Name, LastName
FROM Employees INNER JOIN Departments
ON Employees.Department = Departments.Code
AND Departments.Budget > 60000;
/* With subquery */
SELECT Name, LastName FROM Employees
WHERE Department IN
(SELECT Code FROM Departments WHERE Budget > 60000);
-- 2.13 Select the departments with a budget larger than the average budget of all the departments.
SELECT * FROM Departments
WHERE Budget > (SELECT AVG(Budget) FROM Departments);
-- 2.14 Select the names of departments with more than two employees.
/* With subquery */
SELECT Name FROM Departments
WHERE Code IN (SELECT Department FROM Employees GROUP BY Department HAVING COUNT(*) > 2);
/* With UNION. This assumes that no two departments have the same name */
SELECT Departments.Name FROM Employees INNER JOIN Departments
ON Department = Code
GROUP BY Departments.Name HAVING COUNT(*) > 2;
-- 2.15 Very Important-- Select the name and last name of employees working for departments with second lowest budget.
select name, lastname from employees where department =
( select temp.code from
(select * from departments order by budget limit 2) temp order by temp.budget desc limit 1);
/* With subquery */
SELECT e.Name, e.LastName
FROM Employees e
WHERE e.Department = (SELECT sub.Code FROM
(SELECT * FROM Departments d ORDER BY d.budget LIMIT 2) sub
ORDER BY budget DESC LIMIT 1);
-- 2.16
-- Add a new department called "Quality Assurance", with a budget of $40,000 and departmental code 11.
-- Add an employee called "Mary Moore" in that department, with SSN 847-21-9811.
insert into departments values(11, 'Quality Assurance', 40000);
insert into employees values(847219811, 'Mary', 'Moore', 11);
-- 2.17 Reduce the budget of all departments by 10%.
update departments set budget = 0.9 * budget;
-- 2.18 Reassign all employees from the Research department (code 77) to the IT department (code 14).
update employees set department = 14 where department = 77;
-- 2.19 Delete from the table all employees in the IT department (code 14).
delete from employees where department = 14;
-- 2.20 Delete from the table all employees who work in departments with a budget greater than or equal to $60,000.
delete from employees where department in
(select code from departments where budget >= 60000);
-- 2.21 Delete from the table all employees.
delete from employees;
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