sql - 如何从如下列表中查询：[1,1,1,2,3,4,2,2,5,3]

Question

我只想查询连续重复 3 次的数字，比如这里的 1。但不是 2，因为它不是连续的。

我怎样才能在sql中实现相同的目标？

Answer 1

SQL 表代表无序集（好吧，技术上是多集）。假设您的“列表”存储为表中的行并且有一个排序列，那么您可以使用lead()：

select distinct number
from (select t.*,
             lead(number) over (order by <ordering col>) as next_number,
             lead(number, 2) over (order by <ordering col>) as next_number_2
      from t
     ) t
where number = next_number and number = next_number_2;

Answer 2

如果将数据存储为表中的行，则可以简化和修改 Gordon 的逻辑以进行任意次数的重复：

select distinct number
from t
qualify
   -- same value in the last n rows, n=3
   min(number) over (order by <ordering col> rows 2 preceding) =
   max(number) over (order by <ordering col> rows 2 preceding)
   -- to avoid false positives for the first n-1 rows
and count(number) over (order by <ordering col> rows 2 preceding) = 3