Question

我有一个带有一些参数的存储过程，其中一个参数是'汽车名称'列表。例如

CALL `car_list_inventory`(1,"'Honda','Nissan','BMW','Toyota'");

存储过程的结果返回当前可用的汽车名称的名称，例如if 我是要运行结果的程序

store  cars_available   
----  ----------------          
1      Honda, BMW

确定可用汽车的部分查询

SELECT store, GROUP_CONCAT(DISTINCT cars.model) AS cars_available 
FROM cars 
JOIN cars_avail ON cars.id = cars_avail.id_ref
WHERE cars.id = LAST_INSERT_ID();

我想要做的是添加第二部分，它将返回不可用的汽车，例如，整个结果应该看起来像

 store  cars_available    cars_not_available
 -----  ----------------   ---------------- 
    1      Honda, BMW        Nissan, Toyota

这可能吗？

Answer 1

获取不可用的汽车：

SELECT store, GROUP_CONCAT(DISTINCT cars.model) AS cars_not_available
FROM cars
LEFT JOIN cars_avail ON cars.id = cars_avail.id_ref
WHERE cars_avail.id_ref IS NULL
GROUP BY store

您还可以使用NOT IN：

SELECT store, GROUP_CONCAT(DISTINCT cars.model) AS cars_not_aveilable
FROM cars
WHERE id NOT IN (SELECT id_ref FROM cars_avail)
GROUP BY store

要在一个查询中获取两者，您可以执行以下操作：

SELECT store,
       GROUP_CONCAT(CASE WHEN cars_avail.id_ref IS NOT NULL
                         THEN cars.model
                    END) AS cars_available,
       GROUP_CONCAT(CASE WHEN cars_avail.id_ref IS NULL
                         THEN cars.model
                    END) AS cars_not_available
FROM cars
LEFT JOIN cars_avail ON cars.id = cars_avail.id
GROUP BY store

Answer 2

您正试图让您的问题适合您已选择的API - 这是找到解决方案的错误方法。特别是当您试图打破关系数据库的基本规则之一时：属性（在这种情况下是过程参数）不应该包含多个值。

使用SQL解决变量参数列表问题的正确方法是将值列表放入表中并进行连接。您可以通过解析单个字符串来分割出值来实现这一目标，但我猜测您不会向用户提供原始的MySQL访问权限 - 因此从的用于桥接访问，然后....

INSERT INTO search (session, model, created) VALUES (CONNECTION_ID(), 'Honda', NOW()), (CONNECTION_ID(), 'Nissan', NOW()), (CONNECTION_ID(), 'BMW', NOW()), (CONNECTION_ID(), 'Toyota', NOW()); SELECT store, SUM(IF(cars.model IS NULL, 0, 1)) AS matches, GROUP_CONCAT(cars.model) AS available, GROUP_CONCAT(IF(cars.model IS NULL, search.models, NULL)) AS notavailable FROM search LEFT JOIN cars ON search.model=cars.model AND cars,stock>0 WHERE search.session=CONNECTION_ID() GROUP by store ORDER BY matches; DELETE FROM search WHERE session=CONNECTION_ID();

mysql存储过程查询建议

2 个答案: