feat(exercises): completed all exercises

src/answers.sql

@@ -1,15 +1,119 @@
 -- Your answers here:
 -- 1
+SELECT 
+    c.name AS country_name, 
+    COUNT(s.id) AS total_states
+FROM 
+    states s
+JOIN 
+    countries c
+ON 
+    s.country_id = c.id
+GROUP BY 
+    c.name;
 
 -- 2
+SELECT COUNT(*) AS employees_wothout_bosses
+FROM employees
+WHERE supervisor_id IS NULL;
 
 -- 3
+    SELECT 
+    c.name AS country_name, 
+    o.address AS address, 
+    COUNT(e.id) AS numer_employees
+FROM 
+    offices o
+JOIN 
+    employees e ON o.id = e.office_id
+JOIN 
+    countries c ON o.country_id = c.id	
+GROUP BY 
+    c.name, o.address
+ORDER BY 
+    numer_employees DESC, c.name ASC
+LIMIT 5;
 
 -- 4
+SELECT 
+    s.id AS supervisor_id,
+    COUNT(e.id) AS number_of_employe
+FROM 
+    employees e
+JOIN 
+    employees s ON e.supervisor_id = s.id
+GROUP BY 
+    s.id
+ORDER BY 
+    number_of_employe DESC
+LIMIT 3;
+
 
 -- 5
+SELECT 
+    s.name AS state_name, 
+    COUNT(o.id) AS colorado_offices
+FROM 
+    offices o
+JOIN 
+    states s ON o.state_id = s.id
+GROUP BY 
+    s.name
+HAVING 
+    s.name = 'Colorado';
 
 -- 6
+SELECT 
+    o.name AS office_name,
+    COUNT(e.id) AS number_of_employees
+FROM 
+    offices o
+JOIN 
+    employees e ON o.id = e.office_id
+GROUP BY 
+    o.name
+ORDER BY 
+    number_of_employees DESC;
 
 -- 7
+(
+    SELECT o.address AS office_address, COUNT(*) AS employee_count
+    FROM employees e
+    JOIN offices o ON e.office_id = o.id
+    GROUP BY o.id, o.address
+    ORDER BY employee_count DESC
+    LIMIT 1
+)
+UNION ALL
+(
+    SELECT o.address AS office_address, COUNT(*) AS employee_count
+    FROM employees e
+    JOIN offices o ON e.office_id = o.id
+    GROUP BY o.id, o.address
+    ORDER BY employee_count ASC
+    LIMIT 1
+);
+
+-- 8
 
+SELECT
+    e.uuid AS employee_uuid,
+    CONCAT(e.first_name, ' ', e.last_name) AS full_name,
+    e.email,
+    e.job_title,
+    o.name AS company,
+    s.name AS state_name,
+    c.name AS country_name,
+    CONCAT(b.first_name, ' ', b.last_name) AS boss_name
+FROM
+    employees e
+INNER JOIN
+    offices o ON e.office_id = o.id
+INNER JOIN
+    states s ON o.state_id = s.id
+INNER JOIN
+    countries c ON s.country_id = c.id
+INNER  JOIN
+    employees b ON e.supervisor_id = b.id
+ORDER BY
+    e.id;