如何編寫SQL查詢以從單行中獲取不同的值？

Question

我有一張桌子，這是一張桌子多次交叉產品的結果。現在，我可能在單行中有不同列的副本。我想知道如何編寫A！= B！= C！= D的查詢，其中A，B，C，D是列名。如何編寫SQL查詢以從同一行中選擇唯一值？

Answer 1

您可以通過一個非常複雜的where條款或僅僅通過投入適當的join條件來解決此問題。

下面是一個例子：

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

的Oracle 11g R2架構設置：

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

查詢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 

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 |