mysql - SQL 复合查询 if-else 或 Case 语句

Question

我有一个表，其中包含 Customer_ID、Customer_Name、Address1、Address2、Mail_Address1、Mail_Address2 等。

在某些情况下，Mail_Address1 = 'Same' 或 ''.... 这基本上意味着我需要提取 Address1 + Address2，否则忽略并采用 Mail_Address1 + Mail_Address2。

我的伪 SQL 查询如下所示:-

// The query that would give me all the records with the same address as Address1 for Mailing Address //
    SELECT Customer_ID, Customer_Name, Address1 + ', ' + Address2 as Address, .... 
    FROM Customers
    Where Customer_ID != 0 AND (Mail_Address1 ='Same' or Mail_Address1 ='')

并且

    SELECT Customer_ID, Customer_Name, Mail_Address1 + ', ' + Mail_Address2 as Address, .... 
    FROM Customers
    Where Customer_ID != 0 AND Mail_Address1 !='Same' AND Mail_Address1 !=''

如何组合这两个查询，以便我可以有一个查询，该查询将根据条件选择正确的地址。 (相同或空字符串)。

Answer 1

您考虑过 CASE 语句吗？

SELECT 
CASE 
    WHEN Customer_ID != 0 AND (Mail_Address1 ='Same' OR Mail_Address1 = '')
    THEN Address1 + ', ' + Address2
    ELSE Mail_Address1 + ', ' + Mail_Address2
END AS address
FROM Customers