Distinct

PRQL doesn’t have a specific distinct keyword. Instead, use group and take 1:

from employees
select department
group department (
  take 1
)

SELECT
  DISTINCT department
FROM
  employees

This also works without a linebreak:

from employees
select department
group department (take 1)

SELECT
  DISTINCT department
FROM
  employees

Selecting from each group

We are be able to select a single row from each group by combining group and sort:

# youngest employee from each department
from employees
group department (
  sort age
  take 1
)

WITH table_0 AS (
  SELECT
    employees.*,
    ROW_NUMBER() OVER (
      PARTITION BY department
      ORDER BY
        age
    ) AS _rn_82
  FROM
    employees
)
SELECT
  table_0.*
FROM
  table_0
WHERE
  _rn_82 <= 1

Roadmap

When using Postgres dialect, we are planning to compile:

# youngest employee from each department
from employees
group department (
  sort age
  take 1
)

… to …

SELECT DISTINCT ON (department) *
FROM employees
ORDER BY department, age