“从”多个表，然后“向左联接”另一个表

Question

我有这个查询，可以很好地工作：

SELECT node.id, CONCAT( REPEAT( '       ', (COUNT(parent.name_en) - 1) ), node.name_en) AS name_en_spaced, node.name_en as name_en, node.name_ar as name_ar, node.rgt as rgt,node.lft as lft, node.filter as filter
    FROM category AS node,
        category AS parent
    WHERE node.lft BETWEEN parent.lft AND parent.rgt
    GROUP BY node.id
    ORDER BY node.lft

当我添加LEFT JOIN （我只是想知道product表中是否有与特定category相关的记录，无论它们是多少或多少）：

SELECT p.price,node.id, CONCAT( REPEAT( '       ', (COUNT(parent.name_en) - 1) ), node.name_en) AS name_en_spaced, node.name_en as name_en, node.name_ar as name_ar, node.rgt as rgt,node.lft as lft, node.filter as filter
    FROM category AS node,
        category AS parent
    LEFT JOIN product AS p on node.id = p.category_id
    WHERE node.lft BETWEEN parent.lft AND parent.rgt
    GROUP BY node.id
    ORDER BY node.lft

我收到此错误#1054 - Unknown column 'node.id' in 'on clause'令人困惑。 可以帮我！

Answer 1

您正在混合两种编写联接的方法。 我认为，最好始终指定您的联接，因为在此之后更容易阅读：

SELECT p.price,node.id,
 CONCAT( REPEAT( '       ', (COUNT(parent.name_en) - 1) ), node.name_en) AS name_en_spaced,
 node.name_en as name_en,
 node.name_ar as name_ar,
 node.rgt as rgt,
 node.lft as lft, 
 node.filter as filter
FROM category AS node,
LEFT JOIN category AS parent
   ON node.lft BETWEEN parent.lft AND parent.rgt
    AND node.XXX = parent.XXX
LEFT JOIN product AS p on node.id = p.category_id
GROUP BY node.id
ORDER BY node.lft

Answer 2

您正在混合两种类型的联接（交叉和左联接）。 尝试这个：

SELECT p.price,node.id, CONCAT( REPEAT( '       ', (COUNT(parent.name_en) - 1) ), node.name_en) AS name_en_spaced, node.name_en as name_en, node.name_ar as name_ar, node.rgt as rgt,node.lft as lft, node.filter as filter
    FROM category AS node
    LEFT JOIN category AS parent ON node.id = parent.id
    LEFT JOIN product AS p on node.id = p.category_id
    WHERE node.lft BETWEEN parent.lft AND parent.rgt
    GROUP BY node.id
    ORDER BY node.lft