查詢以獲取MySQL中不同值的計數

Question

我已經在MySQL中嘗試以下查詢，但無法正常工作。

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

您在同一列上進行分組和計數，因此，結果始終為1 。

編輯：

然后只需省略group by子句

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

Answer 2

SELECT COUNT(DISTINCT RADL_REQUEST_MSISDN)
FROM rbt_activation_details_log
WHERE RADL_ACTIVE = 'A'
GROUP BY RADL_REQUEST_MSISDN;

Answer 3

SELECT Count(UNIQUE(radl_request_msisdn))
FROM   rbt_activation_details_log
WHERE  radl_active = 'A'
GROUP  BY radl_request_msisdn  

Answer 4

根據您的查詢：

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

出現時要檢索未按radl_request_msisdn分組的所有不同計數。 如果是這樣，則您可以通過以下方式重寫查詢：

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

相反，如果要分組，查詢將是：

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