计算最后一行，直到列值等于myql中的给定值

Question

假设我的表只有两列;其中一个是AUTO_INCREMENT，另一个是包含在线数据......

A
B
C
A
A

我希望计算最后一行，直到找到给定值。

假设为，

A : 0 (Count From last to reach A)
C : 2 (Count From last to reach C)
B : 3 (Count From last to reach B)

Answer 1

获取每个项目的最高ID，然后计算具有更高ID的行数。

SELECT x.item, IFNULL(COUNT(y.id), 0) as count
FROM (SELECT item, MAX(id) AS lastid
      FROM yourTable
      GROUP BY item) AS x
LEFT JOIN yourTable AS y ON y.id > x.lastid
GROUP BY x.item

DEMO