Question

我有这个表需要（对于每一行）该记录的平均成本以及它所属类别的平均成本。

id      category   cost       num  ave_cost   ave_cost_category
15117012    15    357.00     420      0.85         0.85   
79030402    79    365.00     349      1.04         1.04  
90125402    90    351.20     439      0.80         0.828 
90125146    90    105.00     112      0.9375       0.828

ave_cost_category是我需要计算的列（它当前为null）。我在表格中有ave_cost数据。

Answer 1

UPDATE MyTable
SET
   ave_cost=cost/num,
   ave_cost_category=t1.ave_cost_category
FROM MyTable
INNER JOIN
 (
   SELECT category,avg(ave_cost) as ave_cost_category
   FROM MyTable
   GROUP BY category
) t1 on MyTable.category = t1.category

JOIN中的内部查询计算整个类别的平均成本。

Answer 2

WITH t
     AS (SELECT SUM(cost) OVER (PARTITION BY category) AS c,
                SUM(num)  OVER (PARTITION BY category) AS n,
                *
         FROM   yourtable)
UPDATE t
SET    ave_cost = cost / num,
       ave_cost_category = c / n

Answer 3

您可以使用CTE（公用表格式）计算每个类别的平均成本，并从中更新您的表格：

;WITH CatCost AS
(
    SELECT
       Category,
       SUM(Cost) / (1.0 * SUM(Num)) 'AvgCostCat'
    FROM
       dbo.YourTable
    GROUP BY
       Category
)
UPDATE dbo.YourTable
SET ave_cost_category = cc.AvgCostCat
FROM CatCost
WHERE dbo.YourTable.Category = cc.Category

Answer 4

我建议在表格中创建两个计算列。

create function dbo.fnAveCostCat(@category int)
returns decimal(10,3)
as
begin
    declare @ave decimal(10,3)
    select @ave = AVG(t.cost/t.num)
        from YourTable t
        where t.category = @category
    return @ave
end
go

alter table YourTable
    add ave_cost as cost/num,
        ave_cost_category as dbo.fnAveCostCat(category)
go

Answer 5

也许这会对你有所帮助：

 UPDATE yourTable SET ave_cost_category = x.avgcost FROM 
    yourTable inner JOIN (SELECT category, AVG(ave_cost) AS avgcost 
FROM yourTable GROUP BY category) x
    ON yourTable.category = x.category

Answer 6

更新您的平均费用，请尝试

update mytable set ave_cost = cost / num;

对于每个类别的平均成本，我不确定这是否适用于sql server，但你可以尝试：

update mytable set ave_cost_category = average
from mytable
inner join (
    select category, avg(ave_cost) as average
    from mytable
    group by category
) as averages on table.category = averages.category

用于更新整个类别列的ave_cost的SQL查询

6 个答案: