SQL Practice Lesson 16 of 26

CASE: bucket rows into categories

Every column so far has come back exactly as stored. Sometimes what you want isn't the raw value but a label based on it - "young" instead of 22, "senior" instead of 61. CASE is SQL's inline if/else: it checks a series of conditions in order and returns the first matching branch's value, right inside a SELECT list.

CASE
  WHEN age < 30 THEN 'young'
  WHEN age < 50 THEN 'adult'
  ELSE 'senior'
END

Each WHEN is checked top to bottom; the first one that's true wins, and ELSE catches everything left over. Give the whole expression an alias with AS and it behaves like any other column in your result.

There's a users table: id, name, age.

Your task: return each user's name, age, and a bracket column: 'young' if under 30, 'adult' if under 50, otherwise 'senior'.

You'll practice:

Writing a multi-branch CASE WHEN ... THEN ... ELSE ... END
Aliasing a CASE expression as a normal output column with AS

-- Return name, age, and a bracket ('young' under 30, 'adult' under 50, else 'senior') as bracket.
SELECT name, age FROM users;