MySQL calculation date difference how much

days of difference between #两日期/time:
to_days (end_time)-to_days (start_time)
number of seconds between #两日期/time:
SELECT Unix_timestamp (end_time)-Unix_timestamp (start_time);
Time difference between #两日期/time score:
SELECT sec_to_time (Unix_timestamp (end_time)-Unix_timestamp (start_time));
The best way is to directly use the "+", "-" calculation, the current version is supported.
For example: SELECT * FROM table_name WHERE Logindate < Now () -10 *;

Instance:

Select Sec_to_time (Unix_timestamp ((SELECT createdtime from ' z_2015-09-15 ' WHERE deviceid= ' 460040271516782 ' ORDER by ID DESC limit 1))-Unix_timestamp ((SELECT createdtime from ' z_2015-09-15 ' WHERE deviceid= ' 460040271516782 ' limit 1));

MySQL calculation date difference how much