Question

我有四个表，我想使用SQL查询加入它们并在产品页面上显示产品

Table 1 [table name: A] has product_id and category_id, 
Table 2 [table name: B] has product_id, and our_price,  
Table 3 [table name: C] has product_id, and product_name  
Table 4 [table name: D] has product_id, description, and saving_price.

在这里，我想

join Table A, B, C, and D和SELECT all product's数据from tables B, C, D which category_id = 77 in table A。

我想在产品页面上打印product_name, description, saving_price, and our_price，其类别ID为77.

Answer 1

大概这就是你想要的，虽然很难从你问的方式知道

SELECT
    A.product_id,
    A.category_id,
    B.our_price,
    C.product_name,
    D.description,
    D.saving_price
FROM
    A
    INNER JOIN B ON A.product_id = B.product_id
    INNER JOIN C ON A.product_id = C.product_id
    INNER JOIN D ON A.product_id = D.product_id
WHERE
    A.category_id = 77

以上假设所有表中都存在数据。如果您在某些数据中缺少数据，则可能需要使用LEFT OUTER JOIN

如何使用一个id将四个表连接在一起

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