关于distinct的问题
有张表记录了用户的点击事件，现在我要计算多少用户点击了（重复的不算），有两个字段，一个是subscriber_id一个是list_id,只有subscriber_id和list_id都一样才能代表同一个人，请问要如何统计呢？

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给出更详细的表结构
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select count(distinct list_id) from tablename where list_id=subscriber_idgroup by subscriber_id
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我给的是错的
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select count(*) from tablename group by subscriber_id,list_id order by null
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select count(*) as iddd from table_name where list_id=subscriber_id group by subscriber_id
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select count(1) from table1 where list_id = subscriber_id group by list_id,subscriber_id;
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select count(*) from (select * from tablename group by subscriber_id,list_id order by null)
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如果要排除subscriber_id或list_id的NULL值用下面的语句：
select count(*) from (select count(*) as num from tablename where subscriber_id is not null and list_id is not null group by subscriber_id,list_id) b

如果要subscriber_id和list_id都没有NULL值可以用下面的语句：
select count(*) from (select count(*) as num from tablename group by ubscriber_id,list_id) b
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select sum(cnt) from (select count(*) as cnt form tablename group by subscriber_id,list_id) tmp