计算mysql中两个时间戳之间的时差

I work on a MySQL database table that has a column containing timestamps (Ex. 2014-09-16 09:08:05) of the time I ping different hosts. My question is how could I calculate in minutes the difference between the first ping and the last one for specific hosts? Also how could I specify different timestamps for the start and the end of the difference mentioned above (instead of the first and last ping). Here is an example of the table:I work on a MySQL database table that has a col