限制为累计列数

Question

说我有一个包含3列的表格： id，row_type，row_score

我想选择第一行（或最后一行），但要根据获取的ID的累积得分来限制选择

示例table

id | row_type | row_score
 1          a                  1
 2          a                  1
 3          b                  2
 4          c                  3
 5          a                  1
 6          b                  2
 7          a                  1
...

第一行的结果，累计分数限制为4：

id | row_type | row_score
 1          a                  1
 2          a                  1
 3          b                  2

Answer 1

此查询应执行您想要的操作。它使用变量来保持累积分数，然后在HAVING子句中使用该分数来限制返回的行：

SELECT t1.*, @cum_score := @cum_score + row_score AS cum_score
FROM table1 t1
JOIN (SELECT @cum_score := 0) c
HAVING cum_score <= 4
ORDER BY cum_score

输出：

id  row_type    row_score   cum_score
1   a           1           1
2   a           1           2
3   b           2           4

SQLFiddle Demo

Answer 2

这应该给您想要的结果：

select t1.id, t1.row_type,t1.row_score, SUM(t2.row_score) as sum
from table t1
inner join table t2 
on t1.id >= t2.id
group by t1.id, t1.row_type,t1.row_score
having SUM(t2.row_score)<=4
order by t1.id

谢谢

Rohan Hodarkar