Question

在MySQL数据库中，我正在寻求从符合条件的字段创建列。

这有效：

DROP TABLE IF EXISTS report4;

create TABLE report4 as (
  select

    orders_products.orders_id,

   MAX( IF(products_id = 1, final_price, "-") ) AS Membership,

MAX( IF(products_id = 12, final_price, "-" ) ) AS Donation, 

MAX( IF( products_id = 16, final_price, "-" ) ) AS AHCD     

from orders_products

Group by orders_id M);

select * from report4;

但我还有其他product_id，我希望注入会员和捐赠的新栏目。

ID为2,3,4,5,6,7,8,9,10,11的产品将进入会员资格。 ID为13,14,15,17,18的产品将进入捐赠。

这是次要部分我无法开展工作。关于我需要做什么的想法。

Answer 1

使用以下语法：

MAX( IF(products_id IN (2,3,4,5,6,7,8,9,10,11), final_price, "-") )

Answer 2

将内部查询更改为products_id IN (....)，如下所示

DROP TABLE IF EXISTS report4;    
create TABLE report4 as ( select        
    orders_products.orders_id,
    MAX( IF(products_id IN ( 1,2,3,4,5,6,7,8,9,10,11 ), final_price, "-") ) AS Membership,        
    MAX( IF(products_id IN ( 12,13,14,15,17,18 ), final_price, "-" ) ) AS Donation,        
    MAX( IF( products_id = 16, final_price, "-" ) ) AS AHCD        
    from orders_products        
    Group by orders_id M);    
select * from report4;

或者，您也可以使用products_id = 1 OR products_id = 2 OR ...代替IN

Answer 3

@Lobo的答案适用于您所寻找的内容。但是，如果您必须添加更多产品，则必须不断重做查询，并且它不可扩展。您应该更改数据库以在某处存储 products_type 列，这样您就可以在需要时对产品进行简单的重新分类，并使查询每次都正确运行。

添加一个名为products_types的表格，您可以改为使用此查询：

select
    orders_products.orders_id,
    MAX( IF(pt.types_id = 1, final_price, "-") ) AS Membership,
    MAX( IF(pt.types_id = 2, final_price, "-" ) ) AS Donation, 
    MAX( IF(pt.types_id = 3, final_price, "-" ) ) AS AHCD     
from orders_products
join products_types pt on (pt.products_id = orders_products.products_id)
group by orders_id

我使用的类型的表定义是：

CREATE TABLE `products_types` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `products_id` int(11) DEFAULT NULL,
  `types_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) DEFAULT CHARSET=utf8;

使MAX IF AS适用于多个输入

3 个答案: