MYSQL:将产品分成列 [英] MYSQL: Separate products into columns
本文介绍了MYSQL:将产品分成列的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
这与我之前的帖子 MYSQL:获取数量有关每个订单中的产品.
使用下面的查询,它生成一个表:
Using the query below, it generates a table of:
SELECT o.order_id, o.username, op.product_id, SUM( op.quantity ) as quantity
FROM `orders` o JOIN
orders_products op
ON op.order_id = o.order_id
GROUP BY op.product_id, o.order_id
ORDER BY o.order_id, op.product_id;
_______________________________________________
| order_id | username | product_id | quantity |
-----------------------------------------------
| 1 | bill | 1 | 5 |
-----------------------------------------------
| 1 | bill | 2 | 3 |
-----------------------------------------------
| 1 | bill | 3 | 2 |
-----------------------------------------------
| 2 | sally | 1 | 2 |
-----------------------------------------------
| 3 | jeff | 1 | 6 |
-----------------------------------------------
| 3 | jeff | 2 | 7 |
-----------------------------------------------
如上所示,每个新的 product_id
都分配有自己的行.是否可以为每个 product_id
设置额外的列而不是生成与下面相同的输出的行?
As seen above, each new product_id
is assigned its own row. Is it possible to have additional columns for each product_id
instead of rows generating an output same as the one below?
_______________________________________________________________________
| order_id | username | product_qty_1 | product_qty_2 | product_qty_3 |
-----------------------------------------------------------------------
| 1 | bill | 5 | 3 | 2 |
-----------------------------------------------------------------------
| 2 | sally | 2 | 0 | 0 |
-----------------------------------------------------------------------
| 3 | jeff | 6 | 7 | 0 |
-----------------------------------------------------------------------
我的桌子:
-- Orders
_______________________
| order_id | username |
-----------------------
| 1 | bill |
-----------------------
| 2 | sally |
-----------------------
| 3 | jeff |
-----------------------
-- Products
___________________
| id | product |
-------------------
| 1 | Table |
-------------------
| 2 | Chair |
-------------------
| 3 | Mouse |
-------------------
-- Order Products
___________________________________________
| id | order_id | product_id | quantity |
-------------------------------------------
| 1 | 1 | 1 | 5 |
-------------------------------------------
| 2 | 1 | 2 | 3 |
-------------------------------------------
| 3 | 1 | 3 | 2 |
-------------------------------------------
| 4 | 2 | 1 | 2 |
-------------------------------------------
| 5 | 3 | 1 | 6 |
-------------------------------------------
| 6 | 3 | 2 | 7 |
-------------------------------------------
推荐答案
如果提前知道产品,可以使用条件聚合:
If you know the products in advance, you can use conditional aggregation:
SELECT o.order_id, o.username,
SUM(CASE WHEN op.product_id = 1 THEN op.quantity ELSE 0 END) as quantity1,
SUM(CASE WHEN op.product_id = 2 THEN op.quantity ELSE 0 END) as quantity2,
SUM(CASE WHEN op.product_id = 3 THEN op.quantity ELSE 0 END) as quantity3
FROM `orders` o JOIN
orders_products op
ON op.order_id = o.order_id
GROUP BY o.order_id
ORDER BY o.order_id;
如果您不知道产品 ID,那么您将不得不使用动态 SQL,或者使用 GROUP_CONCAT()
来创建一个包含您想要的信息的字符串.
If you don't know the product ids, then you would have to use dynamic SQL, or perhaps use GROUP_CONCAT()
to create a string with the information you want.
这篇关于MYSQL:将产品分成列的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文