如何在 Mysql 中加入 3 个表

Question

你好，我需要你的帮助。

我有这个数据库架构，我想进行“选择”以返回所有“产品”，其中brands.brand_slug = "acer" 和 categories.category_slug = "laptop em>”。 例如，我想要 Acer 在笔记本电脑类别中制造的所有产品的列表。

我尝试使用此命令行，但显然我收到了所有制造商生产的所有笔记本电脑的列表...

我应该如何进行？

SELECT products.product_slug,
products.product_description,
products.product_img,
products.product_is_on_top,
products.product_title
FROM products
LEFT OUTER JOIN categories ON products.category=categories.category_slug
LEFT OUTER JOIN brand_category ON categories.category_slug=brand_category.category_slug
LEFT OUTER JOIN brands ON brand_category.brand_slug=brands.brand_slug
WHERE brands.brand_slug= "acer"
AND categories.category_slug="laptop"

Answer 1

试试这个

SELECT products.product_slug,
products.product_description,
products.product_img,
products.product_is_on_top,
products.product_title
FROM products
INNER JOIN categories ON products.category=categories.category_slug
INNER JOIN brand_category ON categories.category_slug=brand_category.category_slug
INNER JOIN brands ON brand_category.brand_slug=brands.brand_slug
WHERE brands.brand_slug= 'acer'
AND categories.category_slug='laptop'

Answer 2

SELECT 
    orderNumber,
    orderDate,
    orderLineNumber,
    productName,
    quantityOrdered,
    priceEach
FROM
    orders
INNER JOIN
    orderdetails USING (orderNumber)
INNER JOIN
    products USING (productCode)
ORDER BY 
    orderNumber, 
    orderLineNumber;