LinkedIn Easy Group By Having

Only One
Job
Listing

Find companies with exactly one job listing.

Table Schema

Inspect
Table

interactive

Column	Type	Description
job_id	integer	Unique job posting identifier.
company_id	integer	Identifier for the company posting the job.
title	string	Job listing title.
department	string	Department for the role.
location	string	Job location.
salary	integer	Listed salary.
posted_date	date	Date the job was posted.

Sample Data

Sample Input: job_listings

job_id	company_id	title	department	location	salary	posted_date
1	1	Analyst	Data	NY	60000	2024-01-01
2	1	Engineer	Eng	NY	90000	2024-01-02
3	2	Scientist	Data	SF	120000	2024-01-03
4	2	Manager	Ops	SF	110000	2024-01-04
5	3	Analyst	Data	TX	70000	2024-01-05
6	4	Engineer	Eng	CA	95000	2024-01-06

Expected Output

company_id
3
4

SQL Editor

Waiting for query

company_id
3
4

Hints

Hint 01: Group by company_id.

Hint 02: COUNT(*) tells you how many listings each company has.

Hint 03: HAVING COUNT(*) = 1 keeps companies with exactly one listing.

Solution

Solution is locked until you decide to reveal it. Try the editor first, then open this when you want the reference answer.

SELECT
  company_id
FROM job_listings
GROUP BY company_id
HAVING COUNT(*) = 1;

Explanation

Group rows by company_id.

Count how many listings are in each company group.

Keep groups with exactly one row.