SQL 加入行 table 和列 table

Question

我有两个 table 正在尝试连接（加入）。 Table1是一列table如下：

id	Phone	Name	Description
101	123456	Maria	Abc
102	234567	Daniel	Def

Table2是一行table如下：

id	Attribute	Value
101	Manager	Rudolf
101	Account	456
101	Code	B
102	Manager	Anna
102	Code	B
102	Code	C

我要找的结果是：

id	Phone	Name	Description	Manager	Account	Code
101	123456	Maria	Abc	Rudolf	456	B
102	234567	Daniel	Def	Anna		B,C

Answer 1

您可以加入同一个 table 三次（使用不同的别名）。例如：

select
  p.*,
  a.value as Manager,
  b.value as Account,
  c.value as Cardno
from table1 p
left join table2 a on a.id = p.id and a.attribute = 'Manager'
left join table2 b on b.id = p.id and b.attribute = 'Account'
left join table2 c on c.id = p.id and b.attribute = 'Cardno'

Answer 2

你应该使用 3 次 table 2 来获取 manager 的 3 个属性 inner（始终匹配）和 left join 用于 Account 和 CardNo（不总是匹配）

select a.id, a.phone, a.Name, a.Description b.value, c.value
from table1 a 
inner join table2 b ON a.id = b.id and b.attribute = 'Manager' 
left  join table2 c ON a.id = c.id and c.attribute = 'Account' 
left join table2 d ON a.id = d.id and d.attribute = 'CardNo'

Answer 3

如果您的“行 table”中只有三个唯一属性，那么您可以使用这样的子查询：

SELECT 
t.*,
(SELECT t2.Value FROM Table2 WHERE t2.id = t1.id AND t2.Attribute='Manager') as Manager,
(SELECT t2.Value FROM Table2 WHERE t2.id = t1.id AND t2.Attribute='Account') as Account, 
(SELECT t2.Value FROM Table2 WHERE t2.id = t1.id AND t2.Attribute='Cardno') as Cardno,
FROM Table1 t

如果您有更多独特的属性，那么您应该尝试 views or stored procedure 和临时 table 来生成您想要的 table

SQL 加入行 table 和列 table

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