SQL中的数量偏移

Question

Let us suppose we have following tables

product_id | quantity
1          | 250
2          | 150
3          | 120
4          | 300
5          | 301

How do we know that the item number of 401th in SQL? (the answer should be product_id : 3). The query should return the product_id

Let us assume also the row has been in order

Answer 1

You can use Correlated query to find cummulative sum and then filter range using between to find the required slot:

select product_id
from (
    select a.*,
        coalesce((
                select sum(quantity)
                from your_table b
                where b.product_id < a.product_id
                ), 0) + 1 cquant1,
        (
            select sum(quantity)
            from your_table b
            where b.product_id <= a.product_id
            ) cquant2
    from your_table a
    ) t
where 401 between cquant1 and cquant2;

Demo

You can also use user variable for this:

select *
from (
    select product_id,
        @sum1 := @sum1 + coalesce((
                select quantity
                from your_table x
                where x.product_id < t.product_id
                order by x.product_id desc limit 1
                ), 0) as cquantity1,
        @sum2 := @sum2 + quantity as cquantity2
    from your_table t,
        (select @sum1 := 0, @sum2 := 0) t2
    order by product_id
    ) t
where 401 between cquantity1 and cquantity2;

Demo

Answer 2

In case of ORACLE , this will not work with SQLServer

This is by using LAG and SUM OVER() functions,

SELECT PRODUCT_ID FROM 
(
  SELECT PRODUCT_ID 
    , LAG(CUM_QUAN, 1, 0) OVER (ORDER BY PRODUCT_ID) AS START_QUAN
    , CUM_QUAN END_QUAN
  FROM 
  ( 
    SELECT PRODUCT_ID
      , QUANTITY
      , SUM(QUANTITY) OVER (ORDER BY PRODUCT_ID) AS CUM_QUAN 
    FROM YOUR_TABLE
  )
) WHERE 401 BETWEEN START_QUAN AND END_QUAN

Answer 3

You can do this with variables by getting a cumulative sum. However, Gurv's answer is way too complicated.

I think this is the simplest way:

select t.*
from (select t.*, (@s := @s + quantity) as running_quantity
      from t cross join
           (select @s := 0) params
      order by product_id
     ) t
where 401 < running_quantity and
      401 >= running_quantity - quantity;