Question

我有一个非常棘手的问题

假设我有以下表格

表帐户类型：

Id       Type
 1     Checking
 2      Savings

表 Customer_Account ：

Customer_Id      Account_Type_Id
    450                 1
    450                 2
    451                 1

表 Customer_Account 包含客户ID及其帐户类型ID的列表。 Account_Type_Id是来自AccountType.Id。

的外键

假设在 Customer_Account 表中，名为Josh（id 450）的客户可以拥有两者支票和储蓄帐户，如上所示。我可以通过在 AccountType 表上两次LEFT JOIN来输出此客户的ID和帐户类型：

SELECT CustAccount.Customer_Id AS Id, Account1.Type AS Account_Type_1, Account2.Type AS Account_Type_2
FROM Customer_Account CustAccount
LEFT JOIN AccountType Account1
ON Account1.Id = CustAccount.Account_Type_Id
LEFT JOIN AccountType Account2
ON Account2.Id = CustAccount.Account_Type_Id

输出将是：

 Id        Account_Type_1         Account_Type_2           
450           Checking               Checking 
450           Savings                Savings
451           Checking               Checking

我想要做的是，如果像Josh（id 450）这样的客户两者一个支票和一个储蓄帐户，我想将上面两行数据输出到一行像这样：

 Id        Account_Type_1      Account_Type_2
450           Checking            Savings

而且，如果客户只有一种类型的帐户（例如此处ID为451的客户），我只希望这种类型的帐户出现在相应的列下，如下所示：

 Id        Account_Type_1      Account_Type_2
451           Checking

或者，如果ID为451的客户只有一个储蓄帐户，则输出应为：

Id        Account_Type_1      Account_Type_2
451                              Savings

我希望“检查”仅显示在Accoun_Type_1和Account_Type_2下的“Savings”下。如果我执行GROUP BY CustAccount.Customer_Id，我会得到：

 Id        Account_Type_1      Account_Type_2
450           Checking            Checking
451           Checking            Checking

非常感谢任何专家的帮助。

感谢。

Answer 1

这看起来像是一个完整的外部联接的直接应用程序：

SELECT COALESCE(ac1.id, ac2.id) AS id, ac1.Account_Type_1, ac2.Account_Type_2
  FROM (SELECT c.Customer_ID AS Id, t.Type AS Account_Type_1
          FROM Customer_Account AS c
          JOIN AccountType      AS t ON c.Account_Type_ID = t.ID AND t.ID = 1) AS ac1
  FULL OUTER JOIN
       (SELECT c.Customer_ID AS Id, t.Type AS Account_Type_2
          FROM Customer_Account AS c
          JOIN AccountType      AS t ON c.Account_Type_ID = t.ID AND t.ID = 2) AS ac2
    ON ac1.Id = ac2.Id;

如果您的DBMS不支持FULL OUTER JOIN但支持LEFT OUTER JOIN，那么您可以使用：

SELECT ac0.id, ac1.Account_Type_1, ac2.Account_Type_2
  FROM (SELECT DISTINCT c.Customer_ID AS Id FROM Customer_Account AS c) AS ac0
  LEFT OUTER JOIN
       (SELECT c.Customer_ID AS Id, t.Type AS Account_Type_1
          FROM Customer_Account AS c
          JOIN AccountType      AS t ON c.Account_Type_ID = t.ID AND t.ID = 1) AS ac1
    ON ac0.id = ac1.id
  LEFT OUTER JOIN
       (SELECT c.Customer_ID AS Id, t.Type AS Account_Type_2
          FROM Customer_Account AS c
          JOIN AccountType      AS t ON c.Account_Type_ID = t.ID AND t.ID = 2) AS ac2
    ON ac0.Id = ac2.Id;

第一个子查询生成存在的客户ID列表;第二个生成帐户类型1的列表（检查）;第三个生成帐户类型2的列表（保存）。联接确保每个帐户都得到正确识别。

Answer 2

我认为this可以帮助你

1：Sql Select Query Question. Merge Rows或者

this应该帮助你

Answer 3

为ON子句添加更多条件：

ON Account1.Id = CustAccount.Account_Type_Id and Account1.Account_Type_Id = 1

ON Account2.Id = CustAccount.Account_Type_Id and Account2.Account_Type_Id = 2

将导致输出包括客户持有的帐户。如果他们只有一个帐户，那么另一个帐户类型将为NULL。

编辑：对不起，我没有意识到你没有客户表。您可以创建一个包含不同Customer_Id值列表的临时表，并将其用作JOIN中的第一个表。

select distinct Customer_Id into #Customers
    from Customer_Account

或者说得更直接：

select distinct C.Customer_Id,
    ( select 'Checking' from Customer_Account where Customer_Id = C.CustomerId and Account_type_Id = 1 ) as Account_Type_1,
    ( select 'Savings' from Customer_Account where Customer_Id = C.CustomerId and Account_type_Id = 2 ) as Account_Type_2,
    from Customer_Account as C

将包含相同Id但不同数据的两行合并为一行

3 个答案: