由父母和孩子的Mysql顺序

Question

我想显示按父级排序的查询结果，然后显示子级。 这是我的代码

SELECT * FROM 
mst_category AS parent 
LEFT JOIN mst_category AS child 
ON child.category_parent = parent.category_id
GROUP BY parent.category_id
ORDER BY parent.category_group, COALESCE(parent.category_parent, parent.category_id), parent.category_parent != 0, child.category_id

查询结果：

正如您所看到的，有些孩子没有按父ID排序。我的问题是如何排序？

Answer 1

将您的order by子句简化为您想要的排序顺序：

SELECT 
    parent.category_id as `parent_id`,
    parent.category_group as `parent_group`,
    child.category_id as `child_id`
    child.category_group as `child_group`
FROM mst_category AS parent 
LEFT JOIN mst_category AS child 
    ON child.category_parent = parent.category_id
GROUP BY parent.category_id
ORDER BY parent.category_group, child.category_group

3个级别：

SELECT 
    parent.category_id as `parent_id`,
    parent.category_group as `parent_group`,
    child.category_id as `child_id`
    child.category_group as `child_group`,
    child2.category_id as `child2_id`
    child2.category_group as `child2_group`
FROM mst_category AS parent 
LEFT JOIN mst_category AS child 
    ON child.category_parent = parent.category_id
LEFT JOIN mst_category AS child2
    ON child2.category_parent = child.category_id
WHERE parent.category_id = 0
GROUP BY parent.category_id, child.category_id, child2_category_id
ORDER BY parent.category_group, child.category_group, child2.category_group