计算数据库中的重复值

Question

示例数据库：

userid / value
887 / x
887 / y 
2313 / x
2313 / s
123 / e
2313 / i

我如何得到以下回复？

2313 / 3
887 / 2
123 / 1

Answer 1

select userid, count(*)
from table_name
group by userid

编辑：正如anothershrubbery所说，如果你关心结果的顺序那么：

select userid, count(*) as frequency
from table_name
group by userid
order by frequency desc

Answer 2

将group by与汇总功能count()

一起使用

Answer 3

如果您要检查每个用户ID的值数，可以这样做：

select userid, count(value) as total
from table_name
group by userid
order by total desc

如果您尝试检查每个用户ID的 distinct 值，您可以这样做：

select userid, count(distinct value) as total
from table_name
group by userid
order by total desc