解释查询Mysql

Question

我有以下查询

select count(inspection_result) 
from test 
where (inspection_time between "2015-07-14 00:00:00" and "2015-07-14 00:59:59" )
    and  inspection_result= 0 and  part_type = "39000048"  and location = "1" 

当我执行Explain时，它会给我一个352的确切行，它与计数结果相同。 但是当我执行以下查询的解释时

select count(inspection_result) 
from test 
where (inspection_time between "2015-07-14 00:00:00" and "2015-07-14 00:59:59" )
and  inspection_result= 1 and  part_type = "39000048"  and location = "1"

它显示的行数393397，而输出为71280。 因此，它影响了我的查询速度。任何人都可以帮助我为什么这样的查询行为。