Question

This should be fairly simple but it’s tricky to find the right term to use when searching.

In the query below, I need to select WHERE lang='en' ONLY if WHERE lang='nl_NL' returns nothing. In other words, I want to find all records WHERE script='generic', prioritised by lang=nl_NL

SELECT * FROM international WHERE script='generic' AND (lang = 'nl_NL' OR lang = 'en')

Answer 1

SELECT * FROM international WHERE script = 'generic' AND lang = CASE
  WHEN EXISTS(
    SELECT 1
    FROM   international
    WHERE  script = 'generic'
       AND lang   = 'nl_NL'
    LIMIT  1
  ) THEN 'nl_NL'
  ELSE 'en'
END