DROP TABLE IF EXISTS ranges;
CREATE TABLE ranges (
id int PRIMARY KEY,
start time,
end time,
UNIQUE KEY range_key(start, end)
);
INSERT INTO ranges VALUES (1, "13:21:48", "15:11:12");
SELECT * FROM ranges;
id	start	end
1	13:21:48	15:11:12
DELETE FROM ranges WHERE id = 1;
INSERT INTO ranges VALUES (1, "13:21:48", "15:11:12");
SELECT * FROM ranges;
id	start	end
1	13:21:48	15:11:12
DROP TABLE ranges;
