如何计算MySQL中值的非唯一组合？

Question

我有一个表，其中包含一些旧数据，我怀疑这些旧数据可能有些混乱。 这是一个多对多联接表。

LIST_MEMBERSHIPS
----------------
list_id
address_id

我想运行一个查询，该查询将计算每个list_id - address_id对的出现次数，并显示从最高到最低出现次数中的每一个的出现次数。

我知道必须涉及COUNT()和GROUP BY ，对吗？

Answer 1

select list_id, address_id, count(*) as count
from LIST_MEMBERSHIPS
group by 1, 2
order by 3 desc

您可能会发现添加有用

having count > 1

Answer 2

select count(*), list_id, address_id
from list_membership
group by list_id, address_id
order by count(*) desc