Question

我有一张表，这是多次获取单个表的交叉产品的结果。现在我可能在一行中有属于不同列的重复项。我想知道如何为A！= B编写查询！= C！= D其中A，B，C，D是列名。如何编写SQL查询以从同一行中选择唯一值？

Answer 1

您可以通过非常复杂的where条款或仅通过适当的join条件来解决此问题。

以下是一个例子：

select a.col as a, b.col as b, c.col as c, d.col as d
from table a join
     table b
     on b.col <> a.col join
     table c
     on c.col not in (a.col, b.col) join
     table d
     on d.col not in (a.col, b.col, c.col);

Answer 2

SQL Fiddle

Oracle 11g R2架构设置：

CREATE TABLE test ( val ) AS
SELECT LEVEL
FROM   DUAL
CONNECT BY LEVEL <= 5;

查询1 ：

SELECT A.val AS A_val,
       B.val AS B_val,
       C.val AS C_val,
       D.val AS D_val
FROM   test A
       CROSS JOIN test b
       CROSS JOIN test c
       CROSS JOIN test d
WHERE  A.val NOT IN ( b.val, c.val, d.val )
AND    B.val NOT IN ( c.val, d.val )
AND    C.val <> D.val

<强> Results ：

| A_VAL | B_VAL | C_VAL | D_VAL |
|-------|-------|-------|-------|
|     1 |     2 |     3 |     4 |
|     1 |     2 |     3 |     5 |
|     1 |     2 |     4 |     3 |
|     1 |     2 |     4 |     5 |
|     1 |     2 |     5 |     3 |
|     1 |     2 |     5 |     4 |
|     1 |     3 |     2 |     4 |
|     1 |     3 |     2 |     5 |
|     1 |     3 |     4 |     2 |
|     1 |     3 |     4 |     5 |
|     1 |     3 |     5 |     2 |
|     1 |     3 |     5 |     4 |
|     1 |     4 |     2 |     3 |
|     1 |     4 |     2 |     5 |
|     1 |     4 |     3 |     2 |
|     1 |     4 |     3 |     5 |
|     1 |     4 |     5 |     2 |
|     1 |     4 |     5 |     3 |
|     1 |     5 |     2 |     3 |
|     1 |     5 |     2 |     4 |
|     1 |     5 |     3 |     2 |
|     1 |     5 |     3 |     4 |
|     1 |     5 |     4 |     2 |
|     1 |     5 |     4 |     3 |
|     2 |     1 |     3 |     4 |
|     2 |     1 |     3 |     5 |
|     2 |     1 |     4 |     3 |
|     2 |     1 |     4 |     5 |
|     2 |     1 |     5 |     3 |
|     2 |     1 |     5 |     4 |
|     2 |     3 |     1 |     4 |
|     2 |     3 |     1 |     5 |
|     2 |     3 |     4 |     1 |
|     2 |     3 |     4 |     5 |
|     2 |     3 |     5 |     1 |
|     2 |     3 |     5 |     4 |
|     2 |     4 |     1 |     3 |
|     2 |     4 |     1 |     5 |
|     2 |     4 |     3 |     1 |
|     2 |     4 |     3 |     5 |
|     2 |     4 |     5 |     1 |
|     2 |     4 |     5 |     3 |
|     2 |     5 |     1 |     3 |
|     2 |     5 |     1 |     4 |
|     2 |     5 |     3 |     1 |
|     2 |     5 |     3 |     4 |
|     2 |     5 |     4 |     1 |
|     2 |     5 |     4 |     3 |
|     3 |     1 |     2 |     4 |
|     3 |     1 |     2 |     5 |
|     3 |     1 |     4 |     2 |
|     3 |     1 |     4 |     5 |
|     3 |     1 |     5 |     2 |
|     3 |     1 |     5 |     4 |
|     3 |     2 |     1 |     4 |
|     3 |     2 |     1 |     5 |
|     3 |     2 |     4 |     1 |
|     3 |     2 |     4 |     5 |
|     3 |     2 |     5 |     1 |
|     3 |     2 |     5 |     4 |
|     3 |     4 |     1 |     2 |
|     3 |     4 |     1 |     5 |
|     3 |     4 |     2 |     1 |
|     3 |     4 |     2 |     5 |
|     3 |     4 |     5 |     1 |
|     3 |     4 |     5 |     2 |
|     3 |     5 |     1 |     2 |
|     3 |     5 |     1 |     4 |
|     3 |     5 |     2 |     1 |
|     3 |     5 |     2 |     4 |
|     3 |     5 |     4 |     1 |
|     3 |     5 |     4 |     2 |
|     4 |     1 |     2 |     3 |
|     4 |     1 |     2 |     5 |
|     4 |     1 |     3 |     2 |
|     4 |     1 |     3 |     5 |
|     4 |     1 |     5 |     2 |
|     4 |     1 |     5 |     3 |
|     4 |     2 |     1 |     3 |
|     4 |     2 |     1 |     5 |
|     4 |     2 |     3 |     1 |
|     4 |     2 |     3 |     5 |
|     4 |     2 |     5 |     1 |
|     4 |     2 |     5 |     3 |
|     4 |     3 |     1 |     2 |
|     4 |     3 |     1 |     5 |
|     4 |     3 |     2 |     1 |
|     4 |     3 |     2 |     5 |
|     4 |     3 |     5 |     1 |
|     4 |     3 |     5 |     2 |
|     4 |     5 |     1 |     2 |
|     4 |     5 |     1 |     3 |
|     4 |     5 |     2 |     1 |
|     4 |     5 |     2 |     3 |
|     4 |     5 |     3 |     1 |
|     4 |     5 |     3 |     2 |
|     5 |     1 |     2 |     3 |
|     5 |     1 |     2 |     4 |
|     5 |     1 |     3 |     2 |
|     5 |     1 |     3 |     4 |
|     5 |     1 |     4 |     2 |
|     5 |     1 |     4 |     3 |
|     5 |     2 |     1 |     3 |
|     5 |     2 |     1 |     4 |
|     5 |     2 |     3 |     1 |
|     5 |     2 |     3 |     4 |
|     5 |     2 |     4 |     1 |
|     5 |     2 |     4 |     3 |
|     5 |     3 |     1 |     2 |
|     5 |     3 |     1 |     4 |
|     5 |     3 |     2 |     1 |
|     5 |     3 |     2 |     4 |
|     5 |     3 |     4 |     1 |
|     5 |     3 |     4 |     2 |
|     5 |     4 |     1 |     2 |
|     5 |     4 |     1 |     3 |
|     5 |     4 |     2 |     1 |
|     5 |     4 |     2 |     3 |
|     5 |     4 |     3 |     1 |
|     5 |     4 |     3 |     2 |

如何编写SQL查询以从单行获取不同的值？

2 个答案: