MySQL - 在多个列中查找 10 条记录的 "Max"绝对值？

Question

我有一个看起来像这样的表:

 Country | Item | Col1 | Col2 | Col3 | Col4
 4       | 4    | .152 | .01  | .65  | 1 
 9       | 6    | .145 | .98  | .469 | .001
 56      | 7    | .001 | .987 | .011 | .223
 78      | 2    | -18  | .269 | -.70 | .1

等等。我想从 Col1、Col2、Col3、Col4 中找到前 10 个最大 ABS(条目)。所以在这种情况下，答案是:

-18
1 
.987
.98
-.70
.65
.469
.223 
.... 

等等。但是我该怎么做呢？我遇到了 this其中详细说明了如何仅基于 单个 列和this 找到n 列的最大绝对值。但这只能找到 per each 行的最大值。我怎样才能将两者结合起来？

编辑

按照回答中的建议，我尝试了这样的事情:

SELECT MAX(ABS(`Col1`)) as `absValue` FROM Table1
UNION ALL 
SELECT MAX(ABS(`Col2`)) as `absValue` FROM Table1 
UNION ALL 
SELECT MAX(ABS(`Col3`)) as `absValue` FROM Table1
UNION ALL 
SELECT MAX(ABS(`Col4`)) as `absValue` FROM Table1
ORDER BY `absValue` DESC
LIMIT 10 

但是得到了:

18
1
0.9869999885559082
0.699999988079071

我做错了什么？ SQL Fiddle

任何帮助将不胜感激，谢谢!!

Answer 1

 SELECT  `value` 
 FROM (
           SELECT col1 as `value`  FROM yourTable
           UNION all
           SELECT col2 as `value`  FROM yourTable
           UNION all
           SELECT col3 as `value`  FROM yourTable
           UNION all
           SELECT col4 as `value`  FROM yourTable
      ) T
ORDER BY `value` DESC
LIMIT 10

正如大卫和卡米尔所说，你不需要子查询

SQL DEMO

SELECT col1 as `value`  FROM Table1
UNION all
SELECT col2 as `value`  FROM Table1
UNION all
SELECT col3 as `value`  FROM Table1
UNION all
SELECT col4 as `value`  FROM Table1
ORDER BY `value` DESC
LIMIT 10

在问题编辑之后尝试

SELECT ABS(`Col1`) as `absValue` FROM Table1
UNION ALL 
SELECT ABS(`Col2`) as `absValue` FROM Table1 
UNION ALL 
SELECT ABS(`Col3`) as `absValue` FROM Table1
UNION ALL 
SELECT ABS(`Col4`) as `absValue` FROM Table1
ORDER BY `absValue` DESC
LIMIT 10 

或得到准确的输出

SELECT `Col1` as `value` FROM Table1
UNION ALL 
SELECT `Col2` as `value` FROM Table1 
UNION ALL 
SELECT `Col3` as `value` FROM Table1
UNION ALL 
SELECT `Col4` as `value` FROM Table1
ORDER BY ABS(`value`) DESC
LIMIT 10