mysql - 从条件表中获取 WHERE 子句的条件

Question

我创建了以下简单的DataModel:

我用以下数据填充了表格:

1) 表客户

INSERT INTO test.customer
(CustomerName, Country, RegistrationDate)
VALUES 
("Customer A","DE","2015-05-03"),
("Customer B","US","2015-07-25"), 
("Customer C","US","2016-02-15"), 
("Customer D","DE","2017-09-21"), 
("Customer E","AU","2018-12-07");

2) 表订单

INSERT INTO test.orders
(idCustomer, PaymentMethod, OrderDate, OrderValue)
VALUES 
("1","CreditCard","2015-05-04","500"),
("1","PayPal","2015-11-18","200"), 
("3","PayPal","2017-09-04","300"), 
("2","Invoice","2018-04-30","100");

3) 表标准

INSERT INTO test.criterias
(Country, MinimumOrderValue)
VALUES 
("DE","300"),
("US","150"), 
("AU","200");

之后，我创建了一个查询来根据条件 Country 和 OrderValue 获取Customers 及其Orders :

SELECT 
test.customer.idCustomer, CustomerName, Country,
test.orders.OrderValue

FROM test.customer
LEFT JOIN test.customer_info ON test.customer.idCustomer = test.customer_info.idCustomer
LEFT JOIN test.orders ON test.customer.idCustomer = test.orders.idCustomer

WHERE 
Country = "US" AND OrderValue >= "150"
OR Country = "DE" AND OrderValue >= "300" 
OR country = "AU" AND OrderValue >= "200";

到目前为止，所有这些都运行良好。

---

但是，不应将条件放在 SQL 查询中的 WHERE 子句中，而是应将它们存储在名为 Criterias 的单独表中。然后，查询应该从此表中获取数据并应用它们，就像上面的查询中现在所做的那样。

我必须在代码中更改哪些内容才能实现此目的？

Answer 1

不一定是答案；评论太长了...

一组有效的查询条件可能如下所示...

 WHERE (country = "US" AND OrderValue >= 150)
    OR (country = "DE" AND OrderValue >= 300)
    OR (country = "AU" AND OrderValue >= 200);

...或者确实(尽管可能更慢)...

WHERE (country,ordervalue) IN(('US',150),('DE',300),('AU',200));