CASE

CASE n.eyes
 WHEN 'blue' THEN 1
 WHEN 'brown' THEN 2
 ELSE 3
END

Return THEN value from the matching WHEN value. The ELSE value is optional, and substituted for null if missing.

CASE
 WHEN n.eyes = 'blue' THEN 1
 WHEN n.age < 40 THEN 2
 ELSE 3
END

Return THEN value from the first WHEN predicate evaluating to true. Predicates are evaluated in order.