Question

我遇到了一个包含五个字段的表，引用了一个客户列表。字段（c1，c2等）是另一个表中客户的id。需要一个SQL语句，将客户名称解析为一个在线报告和五个entires。例如：

Table1
ID  Description   C1   C2   C3
1   PartyGroup     2    3    1
2   BeerFolk       1    0    2

Customer table
ID  Name
1   Rob
2   Joe
3   Fred


Output:
ID  Description  Cust1 Cust2  Cust3
1   PartyGroup   Joe   Fred   Rob
2   BeerFolk     Rob          Joe

任何想法都会受到赞赏......

Answer 1

SELECT t1.ID, t1.Description, c1.Name AS Cust1, c2.Name AS Cust2, c3.Name AS Cust3
    FROM Table1 t1
        LEFT JOIN Customer c1
            ON t1.C1 = c1.ID
        LEFT JOIN Customer c2
            ON t1.C2 = c2.ID
        LEFT JOIN Customer c3
            ON t1.C3 = c3.ID

Answer 2

你需要在from子句中多次引用customer表 - 将它们别名为c1，c2，c3等 - 然后正常链接。

与此类似：

select t.id, t.description, c1.name "Cust1", c2.name "Cust2", c3.name "Cuat3"
from table1 t, customer c1, customer c2, customer c3
where t.c1 = c1.id
and t.c2 = c2.id
and t.c3 = c3.id

Answer 3

另一种方法是使用UNION或UNION ALL：

来规范化表

TRANSFORM First(Customer.Name) AS FirstOfName
SELECT Norm.ID, Norm.Description
FROM Customer 
INNER JOIN (
     SELECT ID, Description, "C1" As Cust, C1 As CID 
     FROM table1
     UNION 
     SELECT ID, Description, "C2" As Cust, C2 As CID 
     FROM table1
     UNION 
     SELECT ID, Description, "C3" As Cust, C3 As CID 
     FROM table1) AS Norm 
ON Customer.ID = Norm.CID
GROUP BY Norm.ID, Norm.Description
PIVOT Norm.Cust

具有多个查找的SQL查询

3 个答案: