SQL 对每行中的列进行排序并基于此对行进行排序

Question

我可以使用什么 SQL 选择查询来对每一行进行排序，然后对已排序的行进行排序？

例如：表格标签（c1、c2、c3、c4）

2,5,8,4
2,1,6,7
5,2,9,3

查询必须给出：

1,2,6,7
2,3,5,9
2,4,5,8

Answer 1

这只是开始，也许不是最“干净”的代码，但它会工作

SELECT CASE WHEN C1 < C2 THEN 
                CASE WHEN C1 < C3 THEN C1 ELSE C3 END
            ELSE
                CASE WHEN C2 < C3 THEN C2 ELSE C3 END
       END

From YourTable

这将首先选择最小的元素。 再多三个，你就可以走了.. 获得此结果集后，您可以按第一列排序。

Answer 2

SELECT
MIN(c1, c2, c3, c4) AS new_c1,
CASE MIN(c1, c2, c3, c4) WHEN c1 THEN MIN(c2, c3, c4)
                         WHEN c2 THEN MIN(c1, c3, c4)
                         WHEN c3 THEN MIN(c1, c2, c4)
                         WHEN c4 THEN MIN(c1, c2, c3)
                         END AS new_c2,
CASE MAX(c1, c2, c3, c4) WHEN c1 THEN MAX(c2, c3, c4)
                         WHEN c2 THEN MAX(c1, c3, c4)
                         WHEN c3 THEN MAX(c1, c2, c4)
                         WHEN c4 THEN MAX(c1, c2, c3)
                         END AS new_c3,
MAX(c1, c2, c3, c4) AS new_c4
FROM tab
ORDER BY new_c1, new_c2, new_c3, new_c4

• 看到它在sqlfiddle 中工作
• 有关min() 和max() 函数的信息，请参见here

引用：

请注意，当 max() [和 min()] 有 2 个或更多参数时，它是一个简单的函数，但如果只给定一个参数，则作为聚合函数运行。

Answer 3

可能的解决方案：

CREATE TEMPORARY TABLE nums2
(
   Row int,
   V int
);

INSERT INTO nums2
SELECT *     
FROM
(
    SELECT rowid Row, c1 V FROM nums
    UNION ALL
    SELECT rowid Row, c2 V FROM nums
    UNION ALL
    SELECT rowid Row, c3 V FROM nums
    UNION ALL
    SELECT rowid Row, c4 V FROM nums
) 
ORDER BY Row, V;

SELECT n1.V v1, n2.V v2, n3.V v3, n4.V v4
    FROM nums2 n1
    INNER JOIN nums2 n2 ON n1.Row = n2.Row AND n2.rowid = n1.rowid + 1
    INNER JOIN nums2 n3 ON n1.Row = n3.Row AND n3.rowid = n1.rowid + 2
    INNER JOIN nums2 n4 ON n1.Row = n4.Row AND n4.rowid = n1.rowid + 3
    WHERE ((n1.rowid - 1) % 4 = 0)
    ORDER BY n1.V, n2.V, n3.V, n4.V

它使用一个临时表 (nums2) 来保存“线性化”行，并使用隐藏列 rowid 将行分组。

测试人员：http://sqlfiddle.com/#!7/d0232/38

最后一个选择可以简化一点：

SELECT n1.V v1, n2.V v2, n3.V v3, n4.V v4
    FROM nums2 n1
    INNER JOIN nums2 n2 ON n2.rowid = n1.rowid + 1
    INNER JOIN nums2 n3 ON n3.rowid = n1.rowid + 2
    INNER JOIN nums2 n4 ON n4.rowid = n1.rowid + 3
    WHERE ((n1.rowid - 1) % 4 = 0)
    ORDER BY n1.V, n2.V, n3.V, n4.V

因为WHERE 表达式将“选择”每一行的最小值。

测试人员：http://sqlfiddle.com/#!7/d0232/39

查询很容易扩展。

Answer 4

您可以将表格转为(row_nr, col_nr, value) 格式。然后您可以对其进行排序，并将其还原为(row_nr, val1, val2, val3, val4) 格式。

; with  with_numbers as 
        (
        select  row_number() over (order by c1) rn
        ,       *
        from    tab
        )
,       normalized(rn, nr) as 
        (
        select  rn, c1 from with_numbers
        union all
        select  rn, c2 from with_numbers
        union all
        select  rn, c3 from with_numbers
        union all
        select  rn, c4 from with_numbers
        )
,       normalized_with_number as
        (
        select  row_number() over (partition by rn order by nr) rn2
        ,       *
        from    normalized
        )
,       sorted as
        (
        select  max(case when rn2 = 1 then nr end) c1
        ,       max(case when rn2 = 2 then nr end) c2
        ,       max(case when rn2 = 3 then nr end) c3
        ,       max(case when rn2 = 4 then nr end) c4
        from    normalized_with_number
        group by
                rn      
        )
select  *
from    sorted
order by
        c1
,       c2
,       c3
,       c4

See it working at SQL Fiddle.