SQL Exercises: Find out the number of employees in each department

SQL Aggregate Functions: Exercise-25 with Solution

From the following table, write a SQL query to count the number of employees in each department. Return department code and number of employees.

Sample table: emp_details

 EMP_IDNO EMP_FNAME       EMP_LNAME         EMP_DEPT
--------- --------------- --------------- ----------
   127323 Michale         Robbin                  57
   526689 Carlos          Snares                  63
   843795 Enric           Dosio                   57
   328717 Jhon            Snares                  63
   444527 Joseph          Dosni                   47
   659831 Zanifer         Emily                   47
   847674 Kuleswar        Sitaraman               57
   748681 Henrey          Gabriel                 47
   555935 Alex            Manuel                  57
   539569 George          Mardy                   27
   733843 Mario           Saule                   63
   631548 Alan            Snappy                  27
   839139 Maria           Foster                  57

Sample Solution:

-- This query counts the number of employees in each department ('emp_dept') from the 'emp_details' table.
SELECT emp_dept, COUNT(*)
-- Specifies the table from which to retrieve the data (in this case, 'emp_details').
FROM emp_details
-- Groups the result set by the 'emp_dept' column.
GROUP BY emp_dept;

Output of the Query:

emp_dept		count
27			2
57			5
47			3
63			3

Code Explanation:

The given query in SQL retrieves the number of occurrences (count) of each unique value in the "emp_dept" column from the 'emp_details' table. The result will be a table with two columns: "emp_dept" and "COUNT()".
The "GROUP BY" clause groups the rows in the 'emp_details' table based on the values in the "emp_dept" column.

Relational Algebra Expression:

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