如何计算MySQL中非唯一的值组合？

Question

我有一张包含一些遗留数据的表格，我怀疑这些数据可能有些混乱。这是一个多对多的连接表。

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

我想运行一个查询，它会计算每个list_id - address_id对的出现次数，并显示从最高到最低出现次数的每次出现次数。

我知道它必须涉及COUNT()和GROUP BY，对吧？

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

很有用

having count > 1

Answer 2

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