计算最后一行，直到列值等于myql中的给定值

Question

Suppose My table has only two column; among them one is AUTO_INCREMENT and another contains under line data...

A
B
C
A
A

I want to count last rows until desire given value found.

Suppose For,

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

Get the highest ID for each item, and then count the number of rows that have higher IDs.

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