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Author: kristian9577

12.Subqueries and JOINs - Exercise/joins_exercises.sql

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+-- 1.	Employee Address
+
+SELECT e.employee_id,e.job_title,a.address_id,a.address_text
+FROM employees AS e
+JOIN addresses AS a ON e.address_id = a.address_id
+ORDER BY a.address_id
+LIMIT 5;
+
+-- 2.	Addresses with Towns
+SELECT e.first_name,e.last_name,t.name,a.address_text
+FROM employees AS e
+JOIN addresses AS a
+JOIN towns t ON e.address_id = a.address_id
+AND a.town_id = t.town_id
+ORDER BY e.first_name,e.last_name
+LIMIT 5;
+
+-- 3.	Sales Employee
+SELECT e.employee_id,e.first_name,e.last_name,d.name
+FROM employees AS e
+JOIN departments AS d ON e.department_id = d.department_id
+WHERE d.name = 'Sales'
+ORDER BY e.employee_id DESC;
+
+-- 4.	Employee Departments
+SELECT e.employee_id,e.first_name,e.salary,d.name
+FROM employees AS e
+JOIN departments AS d ON e.department_id = d.department_id
+WHERE e.salary > 15000
+ORDER BY d.department_id DESC
+LIMIT 5;
+
+-- 5.	Employees Without Project
+SELECT e.employee_id,e.first_name
+FROM employees AS e
+LEFT JOIN employees_projects AS ep ON e.employee_id = ep.employee_id
+WHERE ep.project_id IS NULL
+ORDER BY e.employee_id DESC
+LIMIT 3;
+
+-- 6.	Employees Hired After
+SELECT e.first_name,e.last_name,e.hire_date,d.name AS dept_name
+FROM employees AS e
+JOIN departments AS d ON e.department_id = d.department_id
+WHERE d.name IN('Sales','Finance') 
+AND DATE (e.hire_date) > '1999/1/1'
+ORDER BY e.hire_date;
+
+-- 7.	Employees with Project
+SELECT e.employee_id,e.first_name,p.name
+FROM employees AS e
+JOIN employees_projects AS ep ON e.employee_id = ep.employee_id
+JOIN projects AS p ON ep.project_id = p.project_id
+WHERE DATE(p.start_date) > ('2002-08-13')
+AND ISNULL(p.end_date)
+ORDER BY e.first_name,p.name
+LIMIT 5; 
+
+-- 8.	Employee 24
+SELECT e.employee_id,e.first_name,IF(YEAR(p.start_date) >= 2005,NULL,p.name)
+FROM employees AS e
+JOIN employees_projects AS ep ON e.employee_id = ep.employee_id
+JOIN projects AS p ON ep.project_id = p.project_id
+WHERE ep.employee_id = 24
+ORDER BY p.name;
+
+-- 9.	Employee Manager
+SELECT e.employee_id,e.first_name,e.manager_id,m.first_name
+FROM employees AS e
+JOIN employees AS m ON e.manager_id = m.employee_id
+WHERE e.manager_id IN (3,7)
+ORDER BY e.first_name;
+
+
+-- 10.	Employee Summary
+SELECT e.employee_id,
+CONCAT(e.first_name,' ',e.last_name) AS 'employee_name',
+CONCAT(m.first_name,' ',m.last_name) AS 'manager_name',
+d.name AS department_name
+FROM employees AS e
+JOIN employees AS m ON m.employee_id=e.manager_id
+JOIN departments AS d ON e.department_id=d.department_id
+ORDER BY e.employee_id
+LIMIT 5;
+
+-- 11.	Min Average Salary
+
+SELECT MIN(min_avg_salary) AS 'min_average_salary'
+FROM
+(
+ SELECT AVG(salary) AS min_avg_salary
+ FROM employees
+ GROUP BY department_id
+)  AS min_salaries;
+
+USE geography;
+
+-- 12.	Highest Peaks in Bulgaria
+SELECT mk.country_code,m.mountain_range,p.peak_name,p.elevation
+FROM mountains_countries AS mk
+JOIN mountains AS m ON mk.mountain_id=m.id
+JOIN peaks AS p ON m.id=p.mountain_id
+WHERE mk.country_code = 'BG' AND p.elevation>2835
+ORDER BY p.elevation DESC; 
+
+-- 13.	Count Mountain Ranges
+SELECT c.country_code,COUNT(m.mountain_range) AS mountain_range
+FROM countries AS c
+JOIN mountains_countries AS mc ON c.country_code = mc.country_code
+JOIN mountains AS m ON mc.mountain_id = m.id
+WHERE c.country_code IN ('US' , 'BG', 'RU')
+GROUP BY c.country_code
+ORDER BY mountain_range DESC;
+
+-- 14.	Countries with Rivers
+
+SELECT c.country_name,r.river_name
+FROM rivers AS r
+RIGHT JOIN countries_rivers AS cr
+ON r.id=cr.river_id
+RIGHT JOIN countries AS c
+ON cr.country_code=c.country_code
+WHERE continent_code = 'AF'
+ORDER BY country_name ASC
+LIMIT 5;
+
+-- 16.	Countries without any Mountains
+
+SELECT (COUNT(*) - COUNT(mc.mountain_id)) AS country_count  
+FROM countries AS c
+LEFT JOIN mountains_countries As mc
+ON c.country_code = mc.country_code;
+
+-- 17.	Highest Peak and Longest River by Country
+
+SELECT c.country_name, MAX(p.elevation) AS highest_peak_elevation, MAX(r.length) AS longest_river_length
+FROM countries AS c
+LEFT JOIN mountains_countries as mc ON c.country_code = mc.country_code 
+LEFT JOIN peaks AS p ON mc.mountain_id = p.mountain_id
+LEFT JOIN countries_rivers AS cr ON cr.country_code = c.country_code
+LEFT JOIN rivers as r ON r.id = cr.river_id
+GROUP BY c.country_name
+ORDER BY highest_peak_elevation DESC, longest_river_length DESC, c.country_name
+LIMIT 5;