Question

我正在寻找一个有效的查询来返回树的子节点。数据结构是：

  `ct_cid` int(10) unsigned NOT NULL default '0', // the data
  `ct_level` int(10) unsigned NOT NULL default '0', // the level (0 = topmost)
  `ct_parent` int(10) unsigned NOT NULL default '0', // parent ct_cid

我需要确保即使树被破坏或两个节点相互指向为父节点，也不会有无限循环。

Answer 1

在我的博客中查看此条目，了解如何在MySQL中有效地执行此操作：

Hierarchical queries in MySQL: finding loops

您需要创建两个函数：

CREATE FUNCTION hierarchy_connect_by_parent_eq_prior_id_with_level_and_loop(value INT, maxlevel INT) RETURNS INT
NOT DETERMINISTIC
READS SQL DATA
BEGIN
        DECLARE _id INT;
        DECLARE _parent INT;
        DECLARE _next INT;
        DECLARE _i INT;
        DECLARE CONTINUE HANDLER FOR NOT FOUND SET @id = NULL;

        SET _parent = @id;
        SET _id = -1;
        SET _i = 0;

        IF @id IS NULL THEN
                RETURN NULL;
        END IF;

        LOOP
                SELECT  MIN(id)
                INTO    @id
                FROM    t_hierarchy
                WHERE   parent = _parent
                        AND id > _id
                        -- Checking for @start_with in descendants
                        AND id <> @start_with
                        AND COALESCE(@level < maxlevel, TRUE);
                IF @id IS NOT NULL OR _parent = @start_with THEN
                        SET @level = @level + 1;
                        RETURN @id;
                END IF;
                SET @level := @level - 1;
                SELECT  id, parent
                INTO    _id, _parent
                FROM    t_hierarchy
                WHERE   id = _parent;
                SET _i = _i + 1;
        END LOOP;
        RETURN NULL;
END

和

CREATE FUNCTION hierarchy_connect_by_iscycle(node INT) RETURNS INT
NOT DETERMINISTIC
READS SQL DATA
BEGIN
        DECLARE _id INT;
        DECLARE _loop INT;
        DECLARE _node INT;
        DECLARE EXIT HANDLER FOR NOT FOUND RETURN 0;
        SET _id = COALESCE(node, @id);
        SET _loop = 0;
        SET _node = 0;
        LOOP
                SELECT  parent
                INTO    _id
                FROM    t_hierarchy
                WHERE   id = _id;
                IF _id = @start_with THEN
                        SET _loop := _loop + 1;
                END IF;
                IF _id = COALESCE(node, @id) THEN
                        SET _node = _node + 1;
                END IF;
                IF _loop >= 2 THEN
                        RETURN _node;
                END IF;
        END LOOP;
END

会模仿Oracle的{{1}}和CONNECT BY，并在查询中使用它们：

CONNECT_BY_ISCYCLE

Answer 2

这是我的问题。递归查询。

function select_child_ids($parent_id,&$ida) {

    global $sql;

    $items = $sql->select_column("SELECT id FROM test WHERE parent_id = ".$parent_id);

    if ($items) {
        foreach ($items as $id) {
            $ida[] = $id;
            select_child_ids($id,$ida);
        }
    } else {
        return false;
    }
}

注意$ sql是我的类使用mysql的示例。你可以使用自己的。执行后，您可以读取数组$ ida

中的子元素

Answer 3

我使用sql查询，然后循环遍历所有记录以创建所需的数据集。

SELECT 
        *
    FROM 
        category
    ORDER BY 
        name ASC

然后

while ($categoryItem = mysql_fetch_assoc($result_category))
{
    $categoryData['items'][$categoryItem['category_id']] = $categoryItem;
    $categoryData['parents'][$categoryItem['parent_id']][] = $categoryItem['category_id'];
}

这对你有帮助！

获取树的所有子节点的高效查询（mysql）

3 个答案: