SQL Query 根据值/空来计算权重或分配权重

Question

我有一个包含列的表格 - id、x1、x2、x3、x4

如果我有价值观

1,y,y,y,y
2,y,null,n,null
3,y,null,null,null

然后说，我想计算 (1)/(y 的数量) 并将行显示为

1,.25,.25,.25,.25
2,1,0,0,0
3,1,0,0,0

是否可以使用 sql 查询来做到这一点？

Answer 1

这是另一个使用子查询的蛮力攻击。设置一些测试数据：

CREATE TABLE MyTable
 (
   Id   int     not null
  ,Col1 char(1) null
  ,Col2 char(1) null
  ,Col3 char(1) null
  ,Col4 char(1) null
 )

INSERT MyTable
           select 1, 'Y', 'Y', 'Y', 'Y'
 union all select 2, 'Y', null, 'N', null
 union all select 3, 'Y', null, null, null
 union all select 4, null, null, null, null

我使用字符数据作为目标值，但将其设为数字​​应该没有问题。我添加了第四行来检查除以零（感谢 ps！）。所以，

SELECT
   mt.ID
  ,case mt.Col1 when 'Y' then xx.distrib else 0 end
  ,case mt.Col2 when 'Y' then xx.distrib else 0 end
  ,case mt.Col3 when 'Y' then xx.distrib else 0 end
  ,case mt.Col4 when 'Y' then xx.distrib else 0 end
 from MyTable mt
  inner join (select
                ID
                ,1.0 / (  case Col1 when 'Y' then 1 else 0 end
                        + case Col2 when 'Y' then 1 else 0 end
                        + case Col3 when 'Y' then 1 else 0 end
                        + case Col4 when 'Y' then 1 else 0 end) distrib
               from MyTable) xx
   on xx.Id = mt.Id

似乎产生了预期的结果。 （单独运行子查询，你会得到除以零......但老实说，我不知道为什么运行整个查询不会。

Answer 2

这里的幼稚版本是

SELECT 
    id,
    CASE 
    WHEN x1 IS NULL THEN
        0
    WHEN f_eval(x1) + f_eval(x2,0) + f_eval(x3,0) + f_eval(x4,0) = 0 THEN
        -- default value
    ELSE
        1 / (f_eval(x1) + f_eval(x2,0) + f_eval(x3,0) + f_eval(x4,0))
    END,
    -- repeat for each column
FROM
    Table

其中 f_eval 或多或少被定义为：

CREATE FUNCTION f_eval(
      @x_value varchar(1)
BEGIN

    DECLARE @return_val int
    SELECT
        @return_val = 
        case
        WHEN ISNULL(@x_value, 'n') = 'y' THEN
            1
        ELSE
            0
        END

     RETURN @return_val
END

Answer 3

试一试

select 

(SUM(case when x1 is null then 0 else 1 end))* 1.0/ ((SUM(case when x1 is null then 0 else 1 end) + SUM(case when x2 is null then 0 else 1 end)+ SUM(case when x3 is null then 0 else 1 end) + + SUM(case when x4 is null then 0 else 1 end)) * 1.0),
(SUM(case when x2 is null then 0 else 1 end))* 1.0/ ((SUM(case when x1 is null then 0 else 1 end) + SUM(case when x2 is null then 0 else 1 end)+ SUM(case when x3 is null then 0 else 1 end) + + SUM(case when x4 is null then 0 else 1 end)) * 1.0),
(SUM(case when x3 is null then 0 else 1 end))* 1.0/ ((SUM(case when x1 is null then 0 else 1 end) + SUM(case when x2 is null then 0 else 1 end)+ SUM(case when x3 is null then 0 else 1 end) + + SUM(case when x4 is null then 0 else 1 end)) * 1.0),
(SUM(case when x4 is null then 0 else 1 end))* 1.0/ ((SUM(case when x1 is null then 0 else 1 end) + SUM(case when x2 is null then 0 else 1 end)+ SUM(case when x3 is null then 0 else 1 end) + + SUM(case when x4 is null then 0 else 1 end)) * 1.0)
from table group by id

你可能已经确保你不被零除

编辑 2

当分母为 0 和 1 时，再增加一个 case。 你也应该改变

   case when x1 is null then 0 else 1 end

到

 case when x1 = 'y' then 1 else 0 end

Answer 4

试试这个

样本数据

declare  @t table( Id int,Col1 char(1) null,Col2 char(1) null,Col3 char(1) null,Col4 char(1) null)
INSERT @t select 1, 'Y', 'Y', 'Y', 'Y' union all select 2, 'Y', null, null, null
 union all select 3, 'Y', null, null, null  

查询：

select t.id 
 ,case Col1 when 'Y' then LEFT(cast( 1.0/x.cntys as varchar(20)),4) else cast( 0 as varchar(1)) end x1
 ,case Col2 when 'Y' then LEFT(cast( 1.0/x.cntys as varchar(20)),4) else cast( 0 as varchar(1)) end x2
 ,case Col3 when 'Y' then LEFT(cast( 1.0/x.cntys as varchar(20)),4) else cast( 0 as varchar(1)) end x3
 ,case Col4 when 'Y' then LEFT(cast( 1.0/x.cntys as varchar(20)),4) else cast( 0 as varchar(1)) end x4

 from @t t
 join(
 select ROW_NUMBER() over(order by getdate()) rn, 
  COUNT(col1) + COUNT(col2) + COUNT(col3) + COUNT(col4) cntys from @t 
group by id)X
on t.Id = X.rn 

输出：

id x1 x2 x3 x4 
1 0.25 0.25 0.25 0.25 
2 1.00 0 0 0 
3 1.00 0 0 0