没有join怎么把一列拆分成多列呢？

Question

医疗保健：

A	B	ID
582	X	1
582	Y	2
755	123	1
755	456	2
811	abc	1
811	def	2

期望结果：

ID	A	B	C	D	E	F
1	582	X	755	123	811	abc
2	582	Y	755	456	811	def

或

ID	582	755	811
1	X	123	abc
2	Y	456	def

我可以这样做:

SELECT ID, A, B
FROM HealthCare as a
LEFT JOIN (select A as C, B as D from HealthCare where A = 755) as b
    ON a.ID = b.ID
LEFT JOIN (select A as E, B as F from HealthCare where A = 811) as c
    ON a.ID = c.ID 
WHERE A = 582

有什么方法可以在没有连接或更少连接的情况下执行此操作？

Answer 1

如果你不想用JOIN我觉得可以尝试用条件聚合函数来做，尝试在CASE WHEN表达式中加入条件

SELECT ID,
       MAX(CASE WHEN A = 582 THEN A END) 'A',
       MAX(CASE WHEN A = 582 THEN B END) 'B',
       MAX(CASE WHEN A = 755 THEN A END) 'C',
       MAX(CASE WHEN A = 755 THEN B END) 'D',
       MAX(CASE WHEN A = 582 THEN B END) 'E',
       MAX(CASE WHEN A = 811 THEN B END) 'F'
FROM HealthCare 
GROUP BY ID

sqlfiddle

没有join怎么把一列拆分成多列呢？

How can I do without join to split one columns into multiple columns?

sql

sql-server

join