Case

Note

case is currently experimental and may change behavior in the near future

Info

case was previously (PRQL 0.4 to 0.5) called switch and renamed to case in PRQL 0.6.0.

PRQL uses case for both SQL’s CASE and IF statements. Here’s an example:

from employees
derive distance = case [
  city == "Calgary" => 0,
  city == "Edmonton" => 300,
]

SELECT
  *,
  CASE
    WHEN city = 'Calgary' THEN 0
    WHEN city = 'Edmonton' THEN 300
    ELSE NULL
  END AS distance
FROM
  employees

If no condition is met, the value takes a null value. To set a default, use a true condition:

from employees
derive distance = case [
  city == "Calgary" => 0,
  city == "Edmonton" => 300,
  true => "Unknown",
]

SELECT
  *,
  CASE
    WHEN city = 'Calgary' THEN 0
    WHEN city = 'Edmonton' THEN 300
    ELSE 'Unknown'
  END AS distance
FROM
  employees

5.1. Case