mysql - 如何使用 ORDER BY 计算行数直到某个值

Question

我需要使用 ORDER BY 获取某些行的计数。

如何获取行数 orderId = 50 之前是什么 (我看到答案是3，但我需要mysql查询如何得到它)

我有这样的 mysql 查询:

select c.id as customerId, o.id as orderId from orders o
inner join customers c on (c.id=o.customerId)
order by c.id asc, o.id desc

此查询输出:

customerId   orderId
19           36
19           35
19           34
31           50     
31           49
31           48
53           73
53           72

Answer 1

<强> SQL DEMO

SELECT Max(rn)
FROM (
    select customerId, 
           orderId , 
           @row := if( orderid = 50, 
                        null,
                        @row + 1 ) as rn
    from orders o
    cross join ( SELECT @row := 0 ) as vars
    order by customerId asc, orderId  desc
)  t

是否可以使用row_number

SELECT MIN(rn) - 1 as cnt
FROM (
    select customerId, 
           orderId , 
           row_number() over (order by customerId asc, orderId  desc ) as rn
    from orders
) t
WHERE orderId = 50;