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读取数据库图

[英]Reading a database diagram

I've been trying to figure out how to get the products that match a certain category id but I have been unable to figure out how to move from category to products. 我一直在试图找出如何获得与某个类别ID相匹配的产品,但一直无法弄清楚如何从类别转到产品。

How would a query that basically selects all products that match a certain category id look? 基本上选择与某个类别ID匹配的所有产品的查询将如何显示?

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This should work: 这应该工作:

SELECT products.*
FROM products,
     product_category
WHERE product_category.categoryid = CATEGORY_ID
  AND products.catalogid = product_category.catalogid

Or if you prefer a join: 或者,如果您喜欢加入:

SELECT products.*
FROM products
INNER JOIN product_category ON products.catalogid = product_category.catalogid
WHERE product_category.categoryid = CATEGORY_ID

Simply replace CATEGORY_ID by the ID of the category you wish to select. 只需将CATEGORY_ID替换为您想要选择的类别的ID。

product_category is a link table, joining the tables products and product_category together: it contains the catalogid , referencing the ID of the category, and catalogid , referencing the ID of the product. product_category是一个链接表,将表productsproduct_category结合在一起:它包含catalogid (引用类别的ID)和catalogid (引用产品的ID)。

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