SQL Exercise: Number of employee for each job in each department

Last update on December 20 2024 11:40:50 (UTC/GMT +8 hours)

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97. From the following table, write a SQL query to count the number of employees in each designation of a department. Return department id, job name and number of employees.

Sample table: employees

Sample Solution:

SELECT dep_id,
       job_name,
       count(*)
FROM employees
GROUP BY dep_id,
         job_name;

Sample Output:

 dep_id | job_name  | count
--------+-----------+-------
   3001 | MANAGER   |     1
   2001 | ANALYST   |     2
   3001 | SALESMAN  |     4
   1001 | MANAGER   |     1
   1001 | PRESIDENT |     1
   2001 | MANAGER   |     1
   2001 | CLERK     |     2
   1001 | CLERK     |     1
   3001 | CLERK     |     1
(9 rows)

Explanation:

The given query in SQL that retrieves "dep_id" ,"job_name" and the count of employees in each department and job name, but only for those who were hired on or after January 1st, 2022 from the table 'employees'.

It groups the data by the combination of columns "dep_id" and "job_name", and counts the number of records for each combination.

Relational Algebra Expression:

Relational Algebra Tree:

Practice Online

Sample Database: employee

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