Unique Job Titles — DISTINCT in SQL

The problem

Helix Systems' HR team is compiling a skills inventory and needs a complete list of job titles currently active in the organization.

Write a query to return each unique job title held by an employee, with no duplicates.

Assumptions:

The employees table contains every active and former employee at Helix Systems.
The title column records each employee's job title; many employees hold the same title.

Output:

One row per unique job title, with a single column title.

Schema · hr 4 tables

departments

id integer

name text

location text

budget numeric

salaries

id integer

employee_id integer

amount numeric

effective_date date

end_date? date

employees

id integer

name text

email text

department_id integer

manager_id? integer

hire_date date

title text

is_active boolean

job_history

id integer

employee_id integer

title text

department_id integer

start_date date

end_date? date

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Solution query

SELECT DISTINCT
  title
FROM
  employees

The shape

DISTINCT title collapses a column with one row per employee down to the active set of job titles at Helix Systems — 37 rows, one per unique title, from CEO and VP Engineering down through Sales Rep and Recruiter.

Clause by clause

SELECT DISTINCT title returns the unique title values from the rows FROM hands up. The deduplication runs over the full set of titles the candidate rows contribute; two employees who both hold Software Engineer produce one row, not two.
FROM employees is the row source. Every employee — active or former, per the assumptions — contributes their title to the candidate set. The result includes any title that was ever held, even by someone who has since left or been promoted into a different role.

Why this and not a hand-maintained titles list

In many organisations there is a separate canonical list of approved titles somewhere — a job-architecture spreadsheet, an HRIS lookup table. Reading from that list gives the set of titles HR has sanctioned. Running DISTINCT title on employees gives the set of titles that have actually been assigned. The two sets are not always the same: a title might exist in the architecture but be unused, or one might be in use that drifted from the canonical list.

For a skills inventory, the in-use set is the right answer — it reflects what work people are actually doing, not what the architecture document claims they could be doing. The cardinality being 37 instead of 4 doesn't change the shape; DISTINCT doesn't care whether the value space is small or large, it just runs the deduplication over whatever lands in front of it.

You practiced using DISTINCT on a free-text categorical column. The same shape applies whether the values are four (status) or forty (title) — DISTINCT doesn't care about cardinality, only about uniqueness.

Return each unique job title held by an employee, with no duplicates

The shape

Clause by clause

Why this and not a hand-maintained titles list

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