像记录一样分组

Question

我们有一组数据，其中每个 CODE 有 2 条记录。数据示例如下：

TICKER    CODE    SCORE    PRICE    PCF
---------------------------------------
ABC        23       A       100      20
DEF        23       B       200      30
XXX        52       C       300      40
YYY        52       D       400      50
GHI        86       E       500      60
JKL        86       F       600      70
MNO        27       G       700      80
PQR        27       H       800      90

所以，我们需要做的是创建一个查询，它将通过 CODE 将类似记录的列返回到 1 条记录中，如下所示：

CODE,TICKER_1,SCORE_1,PRICE_1,PCF_1,TICKER_2,SCORE_2,PRICE_2,PCF_2
23,ABC,A,100,20,DEF,B,200,30
52,XXX,C,300,40,YYY,D,400,40
86,GHI,E,500,60,JKL,F,600,70
27,MNO,G,700,80,PQR,H,800,90

因此，它们通过 CODE 值组合在一起。

Answer 1

您可以尝试以下分配使用ROW_NUMBER 为每个代码条目分配一个行号，然后使用MAX 和一个case 表达式来过滤每个条目。

例如。

SELECT
    CODE,
    MAX(CASE WHEN rn=1 THEN TICKER END) AS TICKER_1,
    MAX(CASE WHEN rn=1 THEN SCORE END) AS SCORE_1,
    MAX(CASE WHEN rn=1 THEN PRICE END) AS PRICE_1,
    MAX(CASE WHEN rn=1 THEN PCF END) AS PCF_1,
    MAX(CASE WHEN rn=2 THEN TICKER END) AS TICKER_2,
    MAX(CASE WHEN rn=2 THEN SCORE END) AS SCORE_2,
    MAX(CASE WHEN rn=2 THEN PRICE END) AS PRICE_2,
    MAX(CASE WHEN rn=2 THEN PCF END) AS PCF_2
FROM (
    SELECT 
        m.*, 
        ROW_NUMBER() OVER (PARTITION BY CODE ORDER BY TICKER) as rn 
    FROM mytable m
) m1
GROUP BY
    CODE

输出：

CODE	TICKER_1	SCORE_1	PRICE_1	PCF_1	TICKER_2	SCORE_2	PRICE_2	PCF_2
23	ABC	A	100	20	DEF	B	200	30
27	MNO	G	700	80	PQR	H	800	90
52	XXX	C	300	40	YYY	D	400	50
86	GHI	E	500	60	JKL	F	600	70

出于调试目的，子查询的输出

    SELECT 
        m.*, 
        ROW_NUMBER() OVER (PARTITION BY CODE ORDER BY TICKER) as rn 
    FROM mytable m

看起来像这样：

TICKER	CODE	SCORE	PRICE	PCF	RN
ABC	23	A	100	20	1
DEF	23	B	200	30	2
MNO	27	G	700	80	1
PQR	27	H	800	90	2
XXX	52	C	300	40	1
YYY	52	D	400	50	2
GHI	86	E	500	60	1
JKL	86	F	600	70	2

View working demo on db fiddle

值得注意的替代品

• 除了CASE WHEN rn=1 THEN TICKER END，您还可以使用oracle 中的DECODE 函数DECODE(rn,1,TICKER)
• 您也可以使用如下所示的数据透视表（注意。列名与预期结果不同）

WITH cte as (
    SELECT 
        m.*, 
        ROW_NUMBER() OVER (PARTITION BY CODE ORDER BY TICKER) as rn 
    FROM mytable m
)
SELECT * FROM cte 
PIVOT (
    MAX(TICKER) as "TICKER",
    MAX(SCORE) as "SCORE",
    MAX(PRICE) as "PRICE",
    MAX(PCF) as "PCF"
    FOR rn IN (1,2)
)

输出：

CODE	1_TICKER	1_SCORE	1_PRICE	1_PCF	2_TICKER	2_SCORE	2_PRICE	2_PCF
23	ABC	A	100	20	DEF	B	200	30
27	MNO	G	700	80	PQR	H	800	90
52	XXX	C	300	40	YYY	D	400	50
86	GHI	E	500	60	JKL	F	600	70

View working demo on db fiddle here