计算COUNT（*）会导致MySQL

Question

我需要计算从MySQL查询返回的记录数。

SELECT 
    COUNT(sa.facility_hmis) AS deployed
FROM
    facility_service_area sa
GROUP BY sa.facility_hmis 

这会让我说6行作为结果，但我需要它给我一行只有数字计数行，即6

Answer 1

如果你需要的是计算不同facility_hmis的数量，你可以明确地做到这一点，而不计算其他任何事情：

SELECT COUNT(DISTINCT facility_hmis) FROM facility_service_area

Answer 2

使用distinct

SELECT COUNT(distinct facility_hmis) AS deployed FROM facility_service_area

Answer 3

将查询换入另一个// Initilize what to delete $delete_val = array('PLZ'); // Search for the array key and unset foreach($delete_val as $dv){ foreach($field as $key => $object){ $array = (array)$object; if(in_array($dv, $array, true)){ unset($field[$key]); } } } $field = array_values($field); // display $field array var_dump($field);

count()