PostgreSQL Aggregate Functions and Group By: Find the number of jobs available in the employees table

1. Write a query to find the number of jobs available in the employees table.

Sample Solution:

Code:

-- Counting the number of distinct job IDs in the employees table
SELECT COUNT(DISTINCT job_id) 
-- Selecting data from the employees table
FROM employees;

Explanation:

• This SQL code counts the number of distinct job IDs present in the "employees" table.
• The COUNT(DISTINCT job_id) function calculates the number of unique job IDs in the table.
• The result set will contain a single row with the count of distinct job IDs in the employees table.

Sample table: employees

Output:

pg_exercises=# SELECT COUNT(DISTINCT job_id)
pg_exercises-# FROM employees;
 count
-------
    19
(1 row)

Relational Algebra Expression:

Relational Algebra Tree:

Practice Online

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