获取两行之间值不同的列名

Question

我有一张有很多列的桌子。有时我需要找到两行之间的差异。我只需滚动屏幕就可以做到这一点，但它很乏味。我正在寻找一个可以为我执行此操作的查询，例如

SELECT columns_for_id_1 != columns_for_id_2
FROM  xyz
WHERE id in (1,2)

表：

id col1 col2 col3 col4
1  qqq  www  eee  rrr
2  qqq  www  XXX  rrr

结果：

"Different columns: id, col3"

有没有简单的方法可以做到这一点？

更新

另一个想要的例子： 我拥有的（表有超过 50 列，而不仅仅是 7 列）：

Id| Col1 | Col2 | Col3 | Col4 | Col5 | Col6 |
==============================================
1 | aaa  | bbb  | ccc  | ddd  | eee  | fff  |
----------------------------------------------
2 | aaa  | XXX  | ccc  | YYY  | eee  | fff  |

查询：

SELECT *
FROM table
WHERE Id = 1 OR Id = 2 
AND "columns value differs"

查询结果：

"Id, Col2, Col4"

或者类似的东西：

    Id|Col2 |Col4 |
    ===============
    1 |bbb  |ddd  |
    ---------------
    2 |XXX  |YYY  |

现在我必须滚动超过 50 列来查看行是否相同，效率不高且容易出错。我不想像这样的长查询

SELECT (COMPARE Id1.Col1 with Id2.Col1 if different then print "Col1 differs", COMPARE Id1.Col2 with Id2.Col2...) 

因为我自己会更快地比较行;)

Answer 1

类似这样的：

SELECT col, MIN(VAL) AS val1, MAX(val) AS val2
FROM (
SELECT id, val, col
FROM (
   SELECT id,  [col1], [col2], [col3], [col4]
   FROM mytable
   WHERE id IN (1,2)) AS src
UNPIVOT (
   val FOR col IN ([col1], [col2], [col3], [col4])) AS unpvt ) AS t
GROUP BY col 
HAVING MIN(val) <> MAX(val)

输出：

col  val1 val2
================
col3 eee  XXX

Answer 2

尝试这个简单的查询，可能会对您有帮助

    SELECT (CASE WHEN a.col1 <> b.col1 THEN 'Different Col1' 
                 WHEN a.col2 <> b.col2 THEN 'Different Col2' 
                 ...
                 ELSE 'No Different' END) --You can add only required columns here
    FROM xyz AS a 
    INNER JOIN xyz AS b ON b.id = 1 --First Record
    WHERE a.id = 2 --Second record to compare

Answer 3

如果您使用的是 SQL Server 2012，那么您还可以使用 LEAD/LAG 窗口功能来执行此操作。 MSDN 参考在这里 - https://msdn.microsoft.com/en-us/library/hh213125.aspx

select 
id, 
col1,
col2,
col3,
col4,
stuff(diff_cols,len(diff_cols-1),1,'') diff_cols 
from 
(
SELECT 
id, 
col1,
col2,
col3,
col4,
concat
(
'Different columns:',
CASE 
WHEN LEAD(id, 1,0) OVER (ORDER BY id) <> id THEN 'id,'
WHEN LEAD(col1, 1,0) OVER (ORDER BY id) <> col1 THEN 'col1,'
WHEN LEAD(col2, 1,0) OVER (ORDER BY id) <> col2 THEN 'col2,'
WHEN LEAD(col3, 1,0) OVER (ORDER BY id) <> col3 THEN 'col3,'
WHEN LEAD(col4, 1,0) OVER (ORDER BY id) <> col4 THEN 'col4,'
) diff_cols
FROM xyz
) tmp

Answer 4

我喜欢Giorgos Betsos回答的优雅，但它给了我一个“缺少右括号”错误（？），这就是为什么我重构它以使其工作并且对我来说更具可读性。请随意摆弄我的工作示例here或here。

create table a_table
(
    id int,
    col1 varchar(255),
    col2 varchar(255),
    col3 varchar(255),
    col4 varchar(255)
);

insert into a_table values
    (1,'aaa','bbb','ZZZ', 'ddd'),
    (2,'aaa','XXX','ccc', 'YYY'),
    (3,'UUU','bbb','VVV', 'ddd');

WITH orig_data_query AS 
(
    SELECT id, col1, col2, col3, col4
    FROM a_table
    WHERE id IN (1,2)
),
pivot_query AS 
(
    SELECT id, val, col
    FROM orig_data_query
    UNPIVOT
    (
        val FOR col IN (col1, col2, col3, col4)
    )
)
SELECT col, MIN(VAL) AS val1, MAX(val) AS val2
FROM pivot_query
GROUP BY  col
HAVING MIN(val) <> MAX(val);