Question

我对此查询有疑问

SELECT DISTINCT(oth.book) FROM book_meta_keywords oth, 
                (SELECT bmk.meta_keyword AS metaKeyword, bmk.book AS book FROM books b
                    INNER JOIN customers_books cvb ON cvb.book = b.id
                    INNER JOIN book_meta_keywords bmk ON bmk.book = b.id
                    WHERE cvb.customer = 1 ) AS allCustomerPurchasedBooksMeta 
            INNER JOIN books b ON b.id = oth.book
            WHERE oth.meta_keyword = allCustomerPurchasedBooksMeta.metaKeyword AND oth.book != allCustomerPurchasedBooksMeta.book AND b.status = 'GOOD'

对于此查询，我遇到了以下错误。

错误：对表“ oth”的FROM子句条目的引用无效第6行：b.id = oth.book上的INNER JOIN图书 ^ 提示：表“ oth”有一个条目，但是不能从查询的这一部分中引用它。，时间：0.002000秒

但是，如果我运行以下查询，它将起作用

SELECT DISTINCT(oth.book) FROM book_meta_keywords oth, 
                (SELECT bmk.meta_keyword AS metaKeyword, bmk.book AS book FROM books b
                    INNER JOIN customers_books cvb ON cvb.book = b.id
                    INNER JOIN book_meta_keywords bmk ON bmk.book = b.id
                    WHERE cvb.customer = 1 ) AS allCustomerPurchasedBooksMeta 
            WHERE oth.meta_keyword = allCustomerPurchasedBooksMeta.metaKeyword AND oth.book != allCustomerPurchasedBooksMeta.book

任何人都可以帮助我为什么...查询基本上是在尝试根据基于购买的图书的meta关键字来获取相似的图书。

谢谢。

Answer 1

您缺少join

SELECT DISTINCT oth.book FROM book_meta_keywords oth join
                (SELECT bmk.meta_keyword AS metaKeyword, bmk.book AS book FROM books b
                    INNER JOIN customers_books cvb ON cvb.book = b.id
                    INNER JOIN book_meta_keywords bmk ON bmk.book = b.id
                    WHERE cvb.customer = 1 ) AS allCustomerPurchasedBooksMeta 
on oth.meta_keyword = allCustomerPurchasedBooksMeta.metaKeyword and 
   oth.book != allCustomerPurchasedBooksMeta.book
            INNER JOIN books b ON b.id = oth.book
            WHERE  b.status = 'GOOD'

Answer 2

这是您的FROM子句：

FROM 
    book_meta_keywords oth, 
    (SELECT ... FROM ... WHERE ...) AS allCustomerPurchasedBooksMeta 
    INNER JOIN books b ON b.id = oth.book

您正在混合使用显式联接和隐式联接（后者用逗号表示）。别。它们具有不同的优先规则，查询计划者最终会在看到oth之前评估第二个条件。

关于如何解决这个问题：假设逻辑确实是您想要的，那就是横向联接：

FROM 
    book_meta_keywords oth 
    CROSS JOIN LATERAL (SELECT ... FROM ... WHERE ...) AS allCustomerPurchasedBooksMeta 
    INNER JOIN books b ON b.id = oth.book

但是，我怀疑您的查询可以进一步简化。您可能要问另一个问题，以说明查询的目的并提供一个最小的可复制示例。

Answer 3

它可以工作：

SELECT DISTINCT oth.book 
FROM book_meta_keywords oth
     INNER JOIN books b ON b.id = oth.book
     , (SELECT bmk.meta_keyword AS metaKeyword, bmk.book AS book 
        FROM books b
        INNER JOIN customers_books cvb ON cvb.book = b.id
        INNER JOIN book_meta_keywords bmk ON bmk.book = b.id
        WHERE cvb.customer = 1 ) AS allCustomerPurchasedBooksMeta 
WHERE oth.meta_keyword = allCustomerPurchasedBooksMeta.metaKeyword 
     AND oth.book != allCustomerPurchasedBooksMeta.book 
     AND b.status = 'GOOD'

但这能满足您的需求吗？

错误：对表“ oth”的FROM子句条目的引用无效

3 个答案: