SQL 获取最接近数字的值

Question

I need to find the closet value of each number in column Divide from the column Quantity and put the value found in the Value column for both Quantities.

Example: In the column Divide the value of 5166 would be closest to Quantity column value 5000. To keep from using those two values more than once I need to place the value of 5000 in the value column for both numbers, like the example below. Also, is it possible to do this without a loop?

Quantity    Divide  Rank         Value
15500       5166    5            5000
1250        416     5            0
5000        1666    5            5000
12500       4166    4            0
164250      54750   3            0
5250        1750    3            0
6250        2083    3            0
12250       4083    3            0
1750        583     2            0
17000       5666    2            0
2500        833     2            0
11500       3833    2            0
1250        416     1            0

Answer 1

There are a couple of answers here but they both use ctes/complex subqueries. There is a much simpler/faster way by just doing a couple of self joins and a group-by

https://www.db-fiddle.com/f/rM268EYMWuK7yQT3gwSbGE/0

select 
      min(min.quantity) as minQuantityOverDivide
    , t1.divide
    , max(max.quantity) as maxQuantityUnderDivide
    , case 
        when 
            (abs(t1.divide - coalesce(min(min.quantity),0)) 
            <
            abs(t1.divide - coalesce(max(max.quantity),0)))
        then max(max.quantity)
        else min(min.quantity) end as cloestQuantity

from t1
left join (select quantity from t1) min on min.quantity >= t1.divide
left join (select quantity from t1) max on max.quantity < t1.divide

group by    
    t1.divide

Answer 2

If I understood the requirements, 5166 is not closest to 5000 - it's closes to 5250 (delta of 166 vs 84 )

The corresponding query, without loops, shall be (fiddle here: https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=be434e67ba73addba119894a98657f17 ).

(I added a Value_Rank as it's not sure if you want Rank to be kept or recomputed)

select
    Quantity, Divide, Rank, Value,
    dense_rank() over(order by Value) as Value_Rank
from
    (
        select
            Quantity, Divide, Rank,
            --
            case
                when abs(Quantity_let_delta) < abs(Quantity_get_delta) then Divide + Quantity_let_delta
                                                                       else Divide + Quantity_get_delta
            end as Value
        from
        (
            select
                so.Quantity, so.Divide, so.Rank,
                -- There is no LessEqualThan, assume GreaterEqualThan
                max(isnull(so_let.Quantity, so_get.Quantity)) - so.Divide as Quantity_let_delta,
                -- There is no GreaterEqualThan, assume LessEqualThan
                min(isnull(so_get.Quantity, so_let.Quantity)) - so.Divide as Quantity_get_delta
            from
                SO so
                    left outer join SO so_let
                    on so_let.Quantity <= so.Divide
                    --
                    left outer join SO so_get
                    on so_get.Quantity >= so.Divide
            group by so.Quantity, so.Divide, so.Rank
        ) so
    ) result

Or, if by closest you mean the previous closest (fiddle here: https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=b41fb1a3fc11039c7f82926f8816e270 ).

select
    Quantity, Divide, Rank, Value,
    dense_rank() over(order by Value) as Value_Rank
from
    (
        select
            so.Quantity, so.Divide, so.Rank,
            -- There is no LessEqualThan, assume 0
            max(isnull(so_let.Quantity, 0)) as Value
        from
            SO so
                left outer join SO so_let
                on so_let.Quantity <= so.Divide
        group by so.Quantity, so.Divide, so.Rank
    ) result

Answer 3

You don't need a loop, basically you need to find which is lowest difference between the divide and all the quantities (first cte). Then use this distance to find the corresponding record (second cte) and then join with your initial table to get the converted values (final select)

;with cte as (
select t.Divide, min(abs(t2.Quantity-t.Divide)) as ClosestQuantity
from #t1 as t
    cross apply #t1 as t2
group by t.Divide
)
,cte2 as (
select distinct
    t.Divide, t2.Quantity
from #t1 as t
cross apply #t1 as t2
where abs(t2.Quantity-t.Divide) = (select ClosestQuantity from cte as c where c.Divide = t.Divide)
)
select t.Quantity, cte2.Quantity as Divide, t.Rank, t.Value
from #t1 as t
left outer join cte2 on t.Divide = cte2.Divide