加入表格并用指定值替换空值

Question

我正在尝试制作一个可打印页面，其中有指定制造商的所有销售，列出所有产品之间的指定日期。如果没有发生过任何销售，它应该显示0

的表格

// Manufacturer table 
// mid, manufacturer 
// Products table 
// pid, product, ref_manufacturer_id 
// Orders table 
// oid, orderPrice, orderDateTime, ref_product_id 

而且其工作方式查询（无日期限制）

SELECT prod.product, COALESCE(COUNT(pord.oid),0) AS orderCount, 
COALESCE(SUM(pord.orderPrice),0) AS orderSum 
FROM product_manufacturer AS manu 
JOIN product_list AS prod ON prod.ref_manufacturer_id = manu.mid 
LEFT JOIN product_orders AS pord ON pord.ref_product_id = prod.pid 
WHERE manu.mid = :manu_id 
GROUP BY prod.product; 

但只要我加入到WHERE语法

WHERE manu.mid = :manu_id AND DATE(pord.orderDateTime) BETWEEN :orders_start AND :orders_end 

我正在使用PHP PDO连接并验证manu_id是int并且orders_start/end被转换为MySQL日期格式。

但是我试图找出的问题是什么导致了这个问题，当我添加日期限制时，每个没有订购的产品都不会显示在输出上？在创建表

CREATE TABLE product_list (
    pid bigint(20) unsigned NOT NULL AUTO_INCREMENT, 
    product varchar(255) NOT NULL, 
    ref_manufacturer_id bigint(20) unsigned NOT NULL, 
    PRIMARY KEY (pid), 
    KEY ref_manufacturer_id (ref_manufacturer_id) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ; 

CREATE TABLE product_manufacturer (
    mid bigint(20) unsigned NOT NULL AUTO_INCREMENT, 
    manufacturer varchar(255) NOT NULL, 
    PRIMARY KEY (mid), 
    UNIQUE KEY manufacturer (manufacturer) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ; 

CREATE TABLE product_orders (
    oid bigint(20) unsigned NOT NULL AUTO_INCREMENT, 
    orderPrice float(10,2) NOT NULL, 
    orderDatetime timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    red_product_id bigint(20) unsigned NOT NULL, 
    PRIMARY KEY (oid), 
    KEY red_product_id (red_product_id) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ; 

Answer 1

你需要的是对orderDateTime标准移动到连接语句代替where子句，如：

SELECT prod.product, COALESCE(COUNT(pord.oid),0) AS orderCount, 
     COALESCE(SUM(pord.orderPrice),0) AS orderSum 
FROM product_manufacturer AS manu 
JOIN product_list AS prod ON prod.ref_manufacturer_id = manu.mid 
LEFT JOIN product_orders AS pord 
      ON pord.ref_product_id = prod.pid 
      AND DATE(pord.orderDateTime) BETWEEN :orders_start AND :orders_end 
WHERE manu.mid = :manu_id 
GROUP BY prod.product; 

它不WHERE子句中工作的原因是因为NULL值从外返回加入。当product_orders没有一行出现在产品中时，外部联接会为日期字段orderDateTime返回NULL，并且该行将被过滤掉，因为NULL不等于任何内容。

Answer 2

SQL试试这个在where子句。

WHERE manu.mid = :manu_id AND (DATE(pord.orderDateTime) BETWEEN :orders_start AND :orders_end) 

它可能读取第二个AND函数作为另一个where子句，该语句应该返回true。只是一个预感。让我知道这是否有窍门。

Answer 3

我不知道你的特定系统是如何工作的，但它可能是orderDateTime没有设置（即，NULL或其他），直到该产品订购。你可能也想尝试：

WHERE manu.mid = :manu_id AND ((DATE(pord.orderDateTime) BETWEEN :orders_start AND :orders_end) OR pord.orderDateTime=NULL)

如果不是这种情况，你可以给你的时候它要的是没有显示出来的东西orderDateTime值的例子吗？

Answer 4

尝试：

SELECT p.product, 
    COALESCE(o.orderCount, 0) as orderCount, 
    COALESCE(o.orderSum,0) AS orderSum 
FROM product_manufacturer AS m 
JOIN product_list AS p ON p.ref_manufacturer_id = m.mid 
LEFT JOIN (
    SELECT ref_product_id as pid, COUNT(oid) AS orderCount, SUM(orderPrice) AS orderSum 
    FROM product_orders 
    WHERE DATE(orderDateTime) BETWEEN :orders_start AND :orders_end 
    GROUP BY ref_product_id 
) AS o ON p.pid = o.pid 
WHERE m.mid = :manu_id 

编辑：ypercube评论后更正。