在 oracle 中用 Unpivot 替换 union all

Posted 2023-04-12

【中文标题】在 oracle 中用 Unpivot 替换 union all

【英文标题】：Replacing union all with Unpivot in oracle

【发布时间】：2021-05-16 07:53:49

【问题描述】：

我有以下查询：

SELECT COL1,ABC AS COL2,'1' AS SEQ,'GRP 10' AS GRP_NAME,'ABC' AS INPUT_COL_NAME,'NEW1' AS OUTPUT_COL_NAME FROM TABLE1
UNION ALL
SELECT COL1,MNO AS COL2,'2' AS SEQ,'GRP 10' AS GRP_NAME,'MNO' AS INPUT_COL_NAME,'NEW2' AS OUTPUT_COL_NAME FROM TABLE1
UNION ALL
SELECT COL1,XYZ AS COL2,'3' AS SEQ,'GRP 10' AS GRP_NAME,'XYZ' AS INPUT_COL_NAME,'NEW3' AS OUTPUT_COL_NAME FROM TABLE1

输入表数据：

SELECT COL1,COL2 FROM TABLE1

COL1	ABC	MNO	XYZ
1	0	20	100
2	15	50	150

输出是：

COL1	COL2	SEQ	GRP_NAME	INPUT_COL_NAME	OUTPUT_COL_NAME
1	0	1	GRP_NEW	ABC	NEW1
2	15	1	GRP_NEW	ABC	NEW1
1	20	2	GRP_NEW	MNO	NEW2
2	50	2	GRP_NEW	MNO	NEW2
1	100	3	GRP_NEW	XYZ	NEW3
2	150	3	GRP_NEW	XYZ	NEW3

上面的查询可以转化为 PIVOT 查询吗？生成相同的输出。

【参考方案1】：

你想要UNPIVOT（而不是PIVOT）：

SELECT col1,
       col2,
       seq,
       'GRP_NEW' AS grp_name,
       input_col_name,
       output_col_name
FROM   table1
UNPIVOT (
  input_col_name FOR ( col2, seq, output_col_name ) IN (
    abc AS ( 'ABC', 1, 'NEW1' ),
    mno AS ( 'MNO', 2, 'NEW2' ),
    xyz AS ( 'XYZ', 3, 'NEW3' )
  )
)
ORDER BY seq, col1

其中，对于样本数据：

CREATE TABLE table1 ( COL1, ABC, MNO, XYZ ) AS
SELECT 1,  0, 20, 100 FROM DUAL UNION ALL
SELECT 2, 15, 50, 150 FROM DUAL

输出：

COL1	COL2	SEQ	GRP_NAME	INPUT_COL_NAME	OUTPUT_COL_NAME
1	ABC	1	GRP_NEW	0	NEW1
2	ABC	1	GRP_NEW	15	NEW1
1	MNO	2	GRP_NEW	20	NEW2
2	MNO	2	GRP_NEW	50	NEW2
1	XYZ	3	GRP_NEW	100	NEW3
2	XYZ	3	GRP_NEW	150	NEW3

db小提琴here