A bit like a switch statement, but to create new columns on the results. Example:
SELECT type, heart_rate,
CASE
WHEN heart_rate > 220-30 THEN "above max"
WHEN heart_rate > ROUND(0.90 * (220-30)) THEN "above target"
WHEN heart_rate > ROUND(0.50 * (220-30)) THEN "within target"
ELSE "below target"
END as "hr_zone"
FROM exercise_logs;
Will show something like:
| type | heart_rate | hr_zone |
|---|---|---|
| biking | 110 | within target |
| biking | 105 | within target |
| dancing | 120 | within target |
| climbing | 90 | below target |