mysql - 如何在列中显示空白结果的某些文本。数据库

Question

我需要为没有提供第二个地址的任何客户显示“未提供”字样。如果仅向 address2 列提供返回为空白的那些词，我将使用什么？

/* Create a customer list that shows the customer name, address, second address (if the customer does not list a second address, print out "none provided") 
and postal code. */

SELECT CONCAT(first_name," ",last_name) AS Name,
CONCAT(address.address,",",address.address2,",",postal_code) AS Customer_info
FROM customer
INNER JOIN address
ON customer.address_id = address.address_id;

Answer 1

使用IF()函数

CONCAT(address.address, ',', IF(address.address2 != '', address.address2, 'None provided'), ",", postal_code) AS Customer_info