Main branch challenges completed

src/answers.sql

@@ -1,15 +1,81 @@
 -- Your answers here:
 -- 1
+-- Count the total number of states in each country.
+SELECT cou.name name, count(sta.id) count
+FROM countries cou
+RIGHT JOIN states sta ON cou.id = sta.country_id
+GROUP BY cou.name;
 
 -- 2
+-- How many employees do not have supervisores.
+SELECT count(emp.id) employees_without_bosses
+FROM employees emp
+WHERE emp.supervisor_id IS NULL;
 
 -- 3
+-- List the top five offices address with the most amount of employees,
+-- order the result by country and display a column with a counter.
+SELECT cou.name name, ofi.address address, count(emp.id) count
+FROM offices ofi
+RIGHT JOIN employees emp ON ofi.id = emp.office_id
+RIGHT JOIN countries cou ON ofi.country_id = cou.id
+GROUP BY ofi.address, cou.name
+ORDER BY count DESC
+LIMIT 5;
 
 -- 4
+-- Three supervisors with the most amount of employees they are in charge.
+SELECT sup.id supervisor_id, count(emp.id) count
+FROM employees sup
+RIGHT JOIN employees emp ON sup.id = emp.supervisor_id
+WHERE emp.supervisor_id IS NOT NULL
+GROUP BY sup.id
+ORDER BY count DESC
+LIMIT 3;
 
 -- 5
+-- How many offices are in the state of Colorado (United States).
+SELECT count(ofi.id) list_of_office
+FROM offices ofi
+RIGHT JOIN states sta ON ofi.state_id = sta.id
+RIGHT JOIN countries cou ON sta.country_id = cou.id
+WHERE cou.id = 1 AND sta.name = 'Colorado' AND sta.abbr = 'CO';
 
 -- 6
+-- The name of the office with its number of employees
+-- ordered in a desc.
+select ofi.name, count(emp.id) count
+from offices ofi
+RIGHT JOIN employees emp ON ofi.id = emp.office_id
+GROUP BY ofi.name
+ORDER BY count DESC;
 
 -- 7
+-- The office with more and less employees.
+(SELECT ofi.address, count(emp.office_id) count
+FROM employees emp
+LEFT JOIN offices ofi on ofi.id = emp.office_id
+GROUP BY ofi.address
+ORDER BY count DESC
+LIMIT 1)
+UNION ALL
+(SELECT ofi.address, count(emp.office_id) count
+FROM employees emp
+LEFT JOIN offices ofi on ofi.id = emp.office_id
+GROUP BY ofi.address
+ORDER BY count
+LIMIT 1);
 
+-- 8
+-- Show the uuid of the employee, first_name and lastname
+-- combined, email, job_title, the name of the office they belong to,
+-- the name of the country, the name of the state and the name of
+-- the boss (boss_name)
+SELECT emp.uuid uuid, emp.first_name || ' ' || emp.last_name full_name, emp.email email, emp.job_title job_title,
+       ofi.name company, cou.name country, sta.name state,
+       COALESCE(bos.first_name, 'Not Available') boss_name
+FROM employees emp
+RIGHT JOIN offices ofi ON emp.office_id = ofi.id
+RIGHT JOIN countries cou ON cou.id = ofi.country_id
+RIGHT JOIN states sta ON sta.id = ofi.state_id
+INNER JOIN employees bos ON emp.supervisor_id = bos.id;