MySQL: Get start & end timestamp for each day

Question

Similar to the question at MYSQL: Find Start and End Timestamp of a consecutive count, I have a table with similar data:

StatusTime          | Reading   
2014-01-01 0         


        

Answer 1

If it only goes below/above again once per day, you can make the query quite simple; just find the min and max time where it's below, grouping by date.

SELECT
  DATE(statustime) statusdate,
  MIN(CASE WHEN reading<50 THEN statustime ELSE NULL END) start_time,
  MAX(CASE WHEN reading<50 THEN statustime ELSE NULL END) end_time
FROM myTable
GROUP BY statusdate

An SQLfiddle to test with.