MySql Murach的第12章 - 需要AS根据两列是否相等而改变。

Question

我在第12章中使用Murach的MySql。我需要做的是：

*创建一个名为customer_addresses的视图，显示送货和结算 每个客户的地址。 此视图应从Customers表返回这些列：customer_id， email_address，last_name和first_name。 此视图应从Addresses表中返回这些列：bill_line1， bill_line2，bill_city，bill_state，bill_zip，ship_line1，ship_line2，ship_city，ship_state， 和ship_zip。 此视图中的行应按last_name和first_name排序 列。

问题在于所有＆＃34; bill＆＃34;和＆＃34;船舶＆＃34;需要根据customers表中的billing_address_id或shipping_address_id是否与addresses表中的address_id列匹配来创建列。我不知道如何去做这件事。我一直在玩if语句而没有运气。任何人都有和如何让这个工作的想法？

这是我的代码留下的内容，在没有运气的情况下将其分开几次：

CREATE OR REPLACE VIEW customer_addresses
AS 
SELECT c.customer_id, email_address, last_name, 
first_name, 
IF (billing_address_id = address_id, line1, (AS ship_line1)) AS bill_line1,
IF (billing_address_id = address_id, line2, '') AS bill_line2, 
IF (billing_address_id = address_id, city, '') AS bill_city, 
IF (billing_address_id = address_id, state, '') AS bill_state, 
IF (billing_address_id = address_id, zip_code, '') AS bill_zip, 
FROM customers c JOIN addresses a
    ON c.customer_id = a.customer_id
WHERE shipping_address_id = address_id
ORDER BY last_name, first_name;