MySQL Joins Exercises: Get the department name and number of employees in the department
MySQL Joins: Exercise-6 with Solution
Write a MySQL query to get the department name and number of employees in the department.
Sample table: employees
+-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | EMPLOYEE_ID | FIRST_NAME | LAST_NAME | EMAIL | PHONE_NUMBER | HIRE_DATE | JOB_ID | SALARY | COMMISSION_PCT | MANAGER_ID | DEPARTMENT_ID | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | 100 | Steven | King | SKING | 515.123.4567 | 1987-06-17 | AD_PRES | 24000.00 | 0.00 | 0 | 90 | | 101 | Neena | Kochhar | NKOCHHAR | 515.123.4568 | 1987-06-18 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 102 | Lex | De Haan | LDEHAAN | 515.123.4569 | 1987-06-19 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 103 | Alexander | Hunold | AHUNOLD | 590.423.4567 | 1987-06-20 | IT_PROG | 9000.00 | 0.00 | 102 | 60 | | 104 | Bruce | Ernst | BERNST | 590.423.4568 | 1987-06-21 | IT_PROG | 6000.00 | 0.00 | 103 | 60 | | 105 | David | Austin | DAUSTIN | 590.423.4569 | 1987-06-22 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 106 | Valli | Pataballa | VPATABAL | 590.423.4560 | 1987-06-23 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 107 | Diana | Lorentz | DLORENTZ | 590.423.5567 | 1987-06-24 | IT_PROG | 4200.00 | 0.00 | 103 | 60 | | 108 | Nancy | Greenberg | NGREENBE | 515.124.4569 | 1987-06-25 | FI_MGR | 12000.00 | 0.00 | 101 | 100 | ............ | 206 | William | Gietz | WGIETZ | 515.123.8181 | 1987-10-01 | AC_ACCOUNT | 8300.00 | 0.00 | 205 | 110 | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+
Sample table: departments
+---------------+----------------------+------------+-------------+ | DEPARTMENT_ID | DEPARTMENT_NAME | MANAGER_ID | LOCATION_ID | +---------------+----------------------+------------+-------------+ | 10 | Administration | 200 | 1700 | | 20 | Marketing | 201 | 1800 | | 30 | Purchasing | 114 | 1700 | | 40 | Human Resources | 203 | 2400 | | 50 | Shipping | 121 | 1500 | | 60 | IT | 103 | 1400 | | 70 | Public Relations | 204 | 2700 | | 80 | Sales | 145 | 2500 | ......... | 270 | Payroll | 0 | 1700 | +---------------+----------------------+------------+-------------+
Code:
-- This SQL query retrieves the count of employees in each department, along with the department names, from the 'departments' and 'employees' tables.
SELECT
department_name AS 'Department Name', -- Selecting the 'department_name' column from the 'departments' table and aliasing it as 'Department Name'.
COUNT(*) AS 'No of Employees' -- Counting the number of records (employees) in each department and aliasing it as 'No of Employees'.
FROM
departments -- Specifying the 'departments' table.
INNER JOIN
employees -- Performing an inner join with the 'employees' table.
ON
employees.department_id = departments.department_id -- Joining the 'employees' and 'departments' tables based on the 'department_id' column.
GROUP BY
departments.department_id, department_name -- Grouping the result set by department ID and department name.
ORDER BY
department_name; -- Ordering the result set by department name in ascending order.
Explanation:
- This SQL query retrieves the count of employees in each department along with the department names.
- It performs an inner join between the 'departments' and 'employees' tables based on the 'department_id' column to associate employees with their respective departments.
- The 'COUNT(*)' function is used to count the number of records (employees) in each department.
- The 'GROUP BY' clause groups the result set by department ID and department name to apply the aggregate function ('COUNT(*)') correctly.
Sample Output:
Department Name No of Employees Accounting 2 Administration 1 Executive 3 Finance 6 Human Resources 1 IT 5 Marketing 2 Public Relations 1 Purchasing 6 Sales 34 Shipping 45
Go to:
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MySQL Code Editor:
Structure of 'hr' database :
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