在 SQL 中的其他列中查找具有最高值的列

Question

我有一个 table 看起来像这样：

table,
th,
td {
  border: 1px solid black;

<table>
  <tr>
    <th>Customer</th>
    <th>Category 1</th>
    <th>Category 2</th>
    <th>Category 3</th>
    <th>Category 4</th>
  </tr>
  <tr>
    <td>aaaaa@aaa.com</td>
    <td>0</td>
    <td>563</td>
    <td>0</td>
    <td>0</td>
  </tr>
  <tr>
    <td>bbbb@bbb.com</td>
    <td>33</td>
    <td>31</td>
    <td>38</td>
    <td>13</td>
  </tr>
  <tr>
    <td>cccc@ccc.com</td>
    <td>108</td>
    <td>0</td>
    <td>0</td>
    <td>0</td>
  </tr>
  <tr>
    <td>dddd@ddd.com</td>
    <td>0</td>
    <td>7</td>
    <td>0</td>
    <td>11</td>
  </tr>
</table>

我正在尝试插入一个名为 "BestCategory" 的新列，它将显示它们之间具有最高值的类别的名称。

我尝试使用 GREATEST，但我的系统不接受它。

你们能帮帮我吗？

Answer 1

首先你必须使用UNPIVOT来计算每一行的maxValue

然后用一个CASE来select什么BestCategory.

Sql Fiddle Demo

WITH maxValues as 
(
   select
     [Customer], Max(Amount) as TheMax
   from 
     Customer 
     UNPIVOT (Amount for AmountCol in 
              ([Category 1], [Category 2], [Category 3], [Category 4])) as unpvt
   group by [Customer]
)        
select 
    Customer.[Customer], [Category 1], [Category 2], [Category 3], [Category 4], 
    TheMax,
    Case 
        WHEN [Category 1] = TheMax THEN '[Category 1]'
        WHEN [Category 2] = TheMax THEN '[Category 2]'
        WHEN [Category 3] = TheMax THEN '[Category 3]'
        ELSE '[Category 4]'
    END  as BestCategory        
from Customer        
inner join maxValues
   on Customer.[Customer] = maxValues.[Customer]

输出

|      Customer | Category 1 | Category 2 | Category 3 | Category 4 | TheMax | BestCategory |
|---------------|------------|------------|------------|------------|--------|--------------|
| aaaaa@aaa.com |          0 |        563 |          0 |          0 |    563 | [Category 2] |
|  bbbb@bbb.com |         33 |         31 |         38 |         13 |     38 | [Category 3] |
|  cccc@ccc.com |        108 |          0 |          0 |          0 |    108 | [Category 1] |
|  dddd@ddd.com |          0 |          7 |          0 |         11 |     11 | [Category 4] |

Answer 2

如果你想要 "greatest field" 中的列名，你可以使用这个 sqlfiddle example

中的想法

它选择每行具有最大值的列名

SELECT CASE 
        WHEN [category 1] > [category 2]
            AND [category 1] > [category 3]
            AND [category 1] > [category 4]
            THEN '[Category 1]'
        ELSE CASE 
                WHEN [category 2] > [category 1]
                    AND [category 2] > [category 3]
                    AND [category 2] > [category 4]
                    THEN '[Category 2]'
                ELSE CASE 
                        WHEN [category 3] > [category 1]
                            AND [category 3] > [category 2]
                            AND [category 3] > [category 4]
                            THEN '[Category 3]'
                        ELSE '[category 4]'
                        END
                END
        END
FROM customer

在 SQL 中的其他列中查找具有最高值的列

Finding columns with highest value among other columns in SQL

sql

exacttarget