Question

我使用嵌套集模型在iPhone上的本地SQLite数据库中存储大型数据层次结构。我从他们的网站上读到MySQL tech article有关如何执行此操作的信息，但他们建议的（我需要的）查询之一似乎不适用于SQLite，我不知道如何绕过它

SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth
FROM line_items AS node,
    line_items AS parent,
    line_items AS sub_parent,
    (SELECT node.name, (COUNT(parent.name) - 1) AS depth
        FROM line_items AS node,
        line_items AS parent
        WHERE node.lft BETWEEN parent.lft AND parent.rgt
        AND node.name = 'Power Up'
        GROUP BY node.name
        ORDER BY node.lft
    ) AS sub_tree
WHERE node.lft BETWEEN parent.lft AND parent.rgt
    AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt
    AND sub_parent.name = sub_tree.name
GROUP BY node.name
HAVING depth <= 1
ORDER BY node.lft;

SQLite报告sub_tree.name不是列，我认为这是因为它的子查询实现不完整。有没有人对如何解决这个限制有任何想法？

查询的目的是获取给定父节点的所有直接子节点。

Answer 1

尝试在子查询中使用“node.name AS name”，即

SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth
FROM line_items AS node,
    line_items AS parent,
    line_items AS sub_parent,
    (SELECT node.name AS name, (COUNT(parent.name) - 1) AS depth
        FROM line_items AS node,
        line_items AS parent
        WHERE node.lft BETWEEN parent.lft AND parent.rgt
        AND node.name = 'Power Up'
        GROUP BY node.name
        ORDER BY node.lft
    ) AS sub_tree
WHERE node.lft BETWEEN parent.lft AND parent.rgt
    AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt
    AND sub_parent.name = sub_tree.name
GROUP BY node.name
HAVING depth <= 1
ORDER BY node.lft;

至少似乎摆脱了错误。

SQLite查询中的子查询无法正常工作

1 个答案: