php - time difference between two rows - mysql -


i wanted know if there way can calculate time difference between 2 rows. want calculate time difference name -> test etc. name can in order.

i want know if test has 2 times @ row 1 , 3 , @ row 7 , 11, can calculate time difference between these rows? i.e row 1 , 3, , other row 7 , 11.

below image database

enter image description here

try using timediff() , subquery 

select timediff((select `entered_at` `demo_test3` `id`='1'),                (select `entered_at` `demo_test3` `id`='3'))

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