mysql - 查询以获取 MySQL 中不同值的计数

Question

我已经在 MySQL 中尝试了下面的查询，但没有成功。

select count(*)
from (
      select count distinct(RADL_REQUEST_MSISDN)
      from rbt_activation_details_log
      where RADL_ACTIVE ='A'
      group by RADL_REQUEST_MSISDN
     );

Answer 1

select count(distinct column_whose_distinct_values_you_want_to_count) 
from rbt_activation_details_log 
where RADL_ACTIVE ='A' 
group by RADL_REQUEST_MSISDN

您在同一列上进行分组和计数，因此结果总是 1。

编辑:

然后简单地省略group by子句

select count(distinct RADL_REQUEST_MSISDN) 
from rbt_activation_details_log 
where RADL_ACTIVE ='A'