Append

Concatenates two tables together.

Equivalent to UNION ALL in SQL. The number of rows is always the sum of the number of rows from the two input tables. To replicate UNION DISTINCT, see set operations.

PRQL

from employees_1
append employees_2

SQL

SELECT
  *
FROM
  employees_1
UNION
ALL
SELECT
  *
FROM
  employees_2

Remove

experimental

Removes rows that appear in another relation, like EXCEPT ALL. Duplicate rows are removed one-for-one.

PRQL

from employees_1
remove employees_2

SQL

SELECT
  *
FROM
  employees_1 AS t
EXCEPT
  ALL
SELECT
  *
FROM
  employees_2 AS b

Intersection

experimental

PRQL

from employees_1
intersect employees_2

SQL

SELECT
  *
FROM
  employees_1 AS t
INTERSECT
ALL
SELECT
  *
FROM
  employees_2 AS b

Set operations

experimental

To imitate set operations i.e. (UNION, EXCEPT and INTERSECT), you can use the following functions:

let distinct = rel -> (from t = _param.rel | group {t.*} (take 1))
let union = `default_db.bottom` top -> (top | append bottom | distinct)
let except = `default_db.bottom` top -> (top | distinct | remove bottom)
let intersect_distinct = `default_db.bottom` top -> (top | intersect bottom | distinct)

Don’t mind the default_db. and noop, these are compiler implementation detail for now.