Question

我正在进行查询以返回存储在sb_carts表中的所有用户购物车。存储在sb_carts中的产品信息通过两个键product_sku和school_id引用。它需要引用两者来返回具有独特库存水平的独特产品等。

当我执行以下查询时，它返回一行，我期待3行。我已经尝试将内部联接分成两个单独的联接，但这仍然只返回1个结果。仅加入一个键具有所需的结果，但可能重新调整错误的产品。左连接返回3行，但某些数据缺少特定于产品的

以下是我正在做的事情的简化示例

SELECT sb_carts.product_sku
FROM sb_carts 
INNER JOIN sb_products ON sb_products.sku = sb_carts.product_sku 
AND sb_products.school_id = sb_carts.school_id
WHERE sb_carts.order_id = 0 
AND sb_carts.user_id = 2 
GROUP BY sb_carts.cart_id

完整查询看起来像

SELECT COUNT(DISTINCT sb_carts.cart_id) as quantity, 
sb_carts.* FROM sb_carts 
INNER JOIN sb_children ON sb_children.child_id = sb_carts.child_id 
INNER JOIN sb_school_entities ON sb_school_entities.school_id   = sb_children.school_id 
INNER JOIN sb_products ON sb_products.sku = sb_carts.product_sku 
AND sb_products.school_id = sb_carts.school_id LEFT JOIN sb_houses ON sb_children.house_id = sb_houses.id 
LEFT JOIN sb_refund_cart ON sb_carts.cart_id = sb_refund_cart.cart_id 
WHERE sb_carts.order_id = 0 
AND sb_carts.user_id = 2 
GROUP BY sb_carts.child_id, sb_carts.product_sku, sb_carts.school_id 
ORDER BY sb_children.dob_year, sb_children.dob_month, sb_children.dob_day ASC

Answer 1

问题很可能是GROUP BY。即使购物车中有多个产品，每个购物车ID也只会返回一条记录。为了得到你想要的，试试这个：

SELECT sb_carts.cart_id, sb_carts.product_sku
FROM sb_carts 
INNER JOIN sb_products ON sb_products.sku = sb_carts.product_sku 
AND sb_products.school_id = sb_carts.school_id
WHERE sb_carts.order_id = 0 
AND sb_carts.user_id = 2 
ORDER BY sb_carts.cart_id

这将返回两列（购物车ID和SKU）而不是一列，并且一个购物车ID的所有商品将在查询中显示为连续的行。

Answer 2

为什么使用Group By声明？如果您未使用Select Sum中的某个功能，AVG，Group By等对您的porpouse毫无意义。因此，尝试运行不带{{1}}语句的查询： - ）

希望它有所帮助！

桑蒂！ :-)

Answer 3

多个键上的Mysql INNER JOIN：

SELECT * from table1 as t1
INNER JOIN table2 as t2
ON CONCAT(t1.key1, t2.key2)=CONCAT(t2.key1, t2.key2);

我们在这里做的是组合两个键的值，使它看起来像是一把钥匙。

MYSQL内部加入两个表的两个键

3 个答案: