我需要计算从MySQL查询返回的记录数量。
SELECT
COUNT(sa.facility_hmis) AS deployed
FROM
facility_service_area sa
GROUP BY sa.facility_hmis
结果会是6行,但我需要它只给我一个行即6
使用不同的
SELECT COUNT(distinct facility_hmis) AS deployed FROM facility_service_area
如果你只需要计算不同的facility_hmis
的数量,你可以显式地做到这一点,而不需要计算其他任何东西:
SELECT COUNT(DISTINCT facility_hmis) FROM facility_service_area
将查询包入另一个count()
SELECT COUNT(1) from (
SELECT COUNT(sa.facility_hmis) AS deployed FROM facility_service_area sa GROUP BY sa.facility_hmis
)