[英]MYSQL - SELECT products WHERE parent_category is active
假设我们有这样的数据库类别结构
# Categories Table
| category_id | parent_category_id | status |
# Products Table
| product_id | category_id |
仅当 parent_category_id
的活动status = 1
如何才能获得类别中的产品列表?
我想我可以在SELECT
语句中使用一些子查询,但是我不知道怎么做! :(
就像是:
SELECT p.*, (SELECT * FROM ? WHERE ? ) AS x
FROM products AS p
LEFT JOIN categories AS c ON p.category_id = c.category_id
WHERE ...
AND p.product_id = '?'
AND ...
预先感谢您的任何建议!
注意:我使用PHP作为后端语言,以防万一我需要某种数据处理才能传递给mysql查询。
尽量不要使用子查询,因为它会影响加载数据的速度
也许可以帮上忙
SELECT *
FROM categories c
INNER JOIN products p ON p.category_id=c.category_id
WHERE c.status = 1
SELECT p.* FROM products p
INNER JOIN categories child ON child.category_id = p.category_id
INNER JOIN categories parent ON parent.category_id = child.parent_category_id
WHERE parent.status=1
在此示例查询中,我不使用左联接或联接,因为您需要该记录存在才能获取状态。
SELECT
*
FROM
products, categories
WHERE
products.category_id = categories.category_id
AND status = '1'
首先,您必须获得所有活动类别
SELECT child.*
FROM Categories child
JOIN Categories parent
ON child.parent_category_id = parent.category_id
AND parent.status = 1
但是您还需要不带有parent_id的根类别
SELECT *
FROM Categories
WHERE parent_category_id IS NULL
AND status = 1
所以你们两个都
SELECT *
FROM Categories child
JOIN Categories parent
ON child.parent_category_id = parent.category_id
AND parent.status = 1
UNION ALL
SELECT *
FROM Categories
WHERE parent_category_id IS NULL
AND status = 1
现在您获得了这些类别的产品
SELECT *
FROM ( ... UNION ALL ... ) active_categories
JOIN Products
ON active_categories.category_id = Product.category_id
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