Daily Temperature Range

Return each sensor, date and the difference between the highest and lowest temperature that day. Order by sensor, date.

Table schema

Readings(sensor VARCHAR(5), ts DATETIME, temp INT)

Sample data

sensor | ts | temp
S1 | 2026-08-01 10:00:00 | 20
S1 | 2026-08-01 11:00:00 | 27
S1 | 2026-08-01 12:00:00 | 25
S2 | 2026-08-01 10:00:00 | 30
S2 | 2026-08-01 11:00:00 | 31
S2 | 2026-08-02 10:00:00 | 22