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) 表格条件

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

之后，我创建了一个查询以根据条件 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";

到目前为止一切正常。

---

但是，与其在 SQL 查询的 WHERE 子句中包含条件，不如将它们存储在名为 Criterias 的单独表中。然后查询应该从该表中获取数据并像现在在上面的查询中一样应用它们。

我必须更改我的代码才能实现此目标吗？

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(虽然可能更慢)...

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