mysql按照某一個條件進行分組統計，同時又要保證一個相同字段的數據只統計一次

SELECT
    n.pk_id,
    count( DISTINCT r.user_id ) forwardNum 
FROM
    news_info n
    INNER JOIN news_info_record r ON r.type = 1 
    AND r.news_id = n.pk_id 
    AND r.data_active = 0 
    AND n.data_active = 0 
GROUP BY
    r.news_id 

按照news_id分組統計，但是在user_id相同的時候不能統計在內