您可以使用mysql的concat函数：

SELECT *, CONCAT(field1, field2, field3) AS result from tbl;

你可以试试 GROUP_CONCAT 接近。它可以扩展到任意数量的列：

CREATE TABLE testdata(id INT PRIMARY KEY, field1 INT, field2 INT, field3 INT);
INSERT INTO testdata (id, field1, field2, field3) VALUES
(1, 7, 2, 9),
(2, 4, 7, 8),
(3, 6, 3, 2);

SELECT testdata.id, field1, field2, field3, GROUP_CONCAT(rtc.fields ORDER BY fields SEPARATOR '') AS fields_sorted
FROM testdata
INNER JOIN (
    SELECT id, field1 AS fields FROM testdata UNION ALL
    SELECT id, field2 AS fields FROM testdata UNION ALL
    SELECT id, field3 AS fields FROM testdata
) AS rtc ON testdata.id = rtc.id
GROUP BY testdata.id, field1, field2, field3;

输出：

+----+--------+--------+--------+---------------+
| id | field1 | field2 | field3 | fields_sorted |
+----+--------+--------+--------+---------------+
|  1 |      7 |      2 |      9 | 279           |
|  2 |      4 |      7 |      8 | 478           |
|  3 |      6 |      3 |      2 | 236           |
+----+--------+--------+--------+---------------+

一个更优雅的解决方案是从本地人那里获益 json_extract 函数根据值的键按升序提取值。

select json_extract('{"10":10, "5": 5}', '$.*'); // [5, 10]

使用 json_object 函数，并对键和值使用相同的字段
使用按所需顺序提取值 json_extract 更换 [ , , 以及 ] 有空位

select json_extract( json_object(f1, f1, f2, f2, f3, f3), '$.*' )

假设 f1 = 5, f2 = 4 and f3 = 1 ，你得到 [1,4,5] 现在您可以使用replace characters替换不需要的字符

select replace( replace( replace( json_extract( json_object(f1, f1, f2, f2, f3, f3), '$.*' ), '[', ''), ']', ''), ', ', '') from t;

请试试这个解决方案，尽管我还没有测试过。你可以通过做一些小的修补来达到你想要的。任何改进，请在评论中提及。

select id, concat(MIN_VAL, MIDDLE_VAL, MAX_VAL) 
from
   ( SELECT ID,
        (CASE
            WHEN field1 >= field2 AND field1 >= field3 THEN field1
            WHEN field2 >= field1 AND field2 >= field3 THEN field2 
            WHEN field3 >= field1 AND field3 >= field2 THEN field3
            ELSE  field1 END) MAX_VAL

    ,Case When field1 < field2 And field1 < field3 Then field1 
                When field2 < field1 And field2 < field3 Then field2 
                Else field3
                End As MIN_VAL
    ,Case When (field1 >= field2 And field1 <= field3) OR  (field1 <= field2 And field1 >= field3) Then field1 
                When (field2 >= field3 And field2 <= field1) OR (field2 <= field3 And field2 >= field1)Then field2
                 WHEN (field3 >= field1 AND field3 <= field2) OR  (field3 <= field1 AND field3 >= field2) THEN field3 
                Else field1
                End As MIDDLE_VAL

       From table
) int_pass

假设您希望forth列按field2、field1、field3的顺序作为字符串串联
尝试：

select * ,concat(field2,field1,field3) as "result" from tbl;

使用 LEAST , GREATEST 技术上起作用

SELECT field1, field2, field3,
   concat(LEAST(field1,field2,field3), 
   (field1 + field2 + field3) - (GREATEST(field1,field2,field3)+
   LEAST(field1,field2,field3)),
   GREATEST(field1,field2,field3)
   ) 
   from tbl