SQL从不同的表

Question

我有2个表：Customer和SubAccount。
Customer(customerId, customerName, address, city, state)
SubAccount(subAccountID, subAccountName, customerID, subAddress, subCity, subState)
我想选择父客户和他们的每个子账户，如下所示：

+------------+---------------+
| Customer   |  SubAccount   |
+------------+---------------+
| Customer1  |  null         |
| Customer1  |  SubAccount1  |
| Customer1  |  SubAccount2  |
| Customer2  |  null         |
| Customer2  |  SubAccount1  |
| Customer3  |  null         |
| Customer3  |  SubAccount1  |
+------------+---------------+

然而，做一个简单的

SELECT Customer.CustomerName, SubAccount.subAccountName
FROM Customer
LEFT JOIN SubAccount ON SubAccount.CustomerId = Customer.CustomerID

不起作用。它只显示

+------------+---------------+
| Customer   |  SubAccount   |
+------------+---------------+
| Customer1  |  SubAccount1  |
| Customer1  |  SubAccount2  |
| Customer2  |  SubAccount1  |
| Customer3  |  SubAccount1  |
+------------+---------------+

进行选择的正确方法是什么？

Answer 1

UNION ALL您现有的查询，其中一个简单的查询从Customers表中选择CustomerName和NULL（AS SubAccount）（无连接）。