MySQL在第二次加入时抛出错误

Question

我收到以下错误：

#1064 - 您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，以了解在 'JOIN product_catalog ON product_catalog.entity_id

附近使用的正确语法

作为以下查询的结果：

SELECT sales_order.created_at , order_item.order_id, sales_order.increment_id, SUM(order_item.qty_ordered) AS qty_ordered , COUNT( * ) 

FROM order_item

JOIN sales_order
ON sales_order.entity_id = order_item.order_id
WHERE sales_order.created_at > '2012-11-15 00:00:00'

JOIN product_catalog
ON product_catalog.entity_id = order_item.product_id
WHERE product_catalog.size = 14

GROUP BY order_item.order_id;

过去，此查询的变体可用于按销售订单对不同类型的产品进行分组，我只需要执行一个JOIN 即可获得所需的所有信息。我遇到的问题来自第二个JOIN。显然我错过了一些东西，但我真的不确定是什么。 :(

Answer 1

请确保WHERE 条件毕竟必须是JOIN

SELECT sales_order.created_at , order_item.order_id, sales_order.increment_id, SUM(order_item.qty_ordered) AS qty_ordered , COUNT( * ) 

FROM order_item

JOIN sales_order
ON sales_order.entity_id = order_item.order_id

JOIN product_catalog
ON product_catalog.entity_id = order_item.product_id

WHERE product_catalog.size = 14
AND sales_order.created_at > '2012-11-15 00:00:00'
GROUP BY order_item.order_id;

首先你必须JOIN你需要的桌子。然后在WHERE 子句之后出现条件。

Answer 2

您的WHERE 子句位于错误的位置。请参阅下面的代码以了解正确的 JOIN 语法。

SELECT sales_order.created_at, 
    order_item.order_id, 
    sales_order.increment_id, 
    SUM(order_item.qty_ordered) AS qty_ordered, 
    COUNT( * )
FROM order_item
JOIN sales_order
    ON sales_order.entity_id = order_item.order_id
    AND sales_order.created_at > '2012-11-15 00:00:00'
JOIN product_catalog
    ON product_catalog.entity_id = order_item.product_id
    AND product_catalog.size = 14
GROUP BY order_item.order_id

Answer 3

JOIN...ON... 子句也是输入条件的部分，因此您不需要 where 子句，只需添加 AND 即可。

SELECT sales_order.created_at , order_item.order_id, sales_order.increment_id, 
       SUM(order_item.qty_ordered) AS qty_ordered , COUNT( * )     
FROM order_item    
JOIN sales_order ON sales_order.entity_id = order_item.order_id
                 and sales_order.created_at > '2012-11-15 00:00:00'
JOIN product_catalog ON product_catalog.entity_id = order_item.product_id
                     and product_catalog.size = 14
GROUP BY order_item.order_id;

请考虑下面的示例，我添加了别名。使用它是一个好习惯，因为代码更具可读性。

SELECT SO.created_at , OI.order_id, SO.increment_id, 
       SUM(OI.qty_ordered) AS qty_ordered , COUNT( * )     
FROM order_item  OI  
JOIN sales_order SO ON SO.entity_id = OI.order_id
                 and SO.created_at > '2012-11-15 00:00:00'
JOIN product_catalog PC ON PC.entity_id = OI.product_id
                     and PS.size = 14
GROUP BY OI.order_id;