MySQL父级

本文介绍了MySQL父级->子查询的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在使用mySQL，并且处于一种情况下，我需要从一个表中选择与父表->另一表中的子数据层次结构中任何级别的ID匹配的表中的数据.

此外，我想通过编写良好的SQL查询而不是PHP代码中的递归函数来解决此问题，因为此功能将被大量使用.

我确实尝试搜索，但偶然发现了许多类似的问题(大多数问题已得到解决)，但是没有一个问题对我有帮助.

为帮助说明情况，这是我当前的设置

表格文章":

• article_id
• category_id
• ...

表格类别

• category_id
• parent_id
• ...

我需要从"articles.category_id"为10的"articles"中选择所有文章.还要从"categories.category_id" 10所属的树中接收所有类别的所有文章. /p>

意思是，其中"10"是父母及其所有孩子，向上则是10是孩子及其所有父母.

可能没有递归的php函数吗?

谢谢.

解决方案

在MySQL中可以做到这一点，但需要一些努力.您必须编写这样的函数:

CREATE FUNCTION hierarchy_connect_by_parent_eq_prior_id(value INT) RETURNS INT NOT DETERMINISTIC READS SQL DATA BEGIN DECLARE _id INT; DECLARE _parent INT; DECLARE _next INT; DECLARE CONTINUE HANDLER FOR NOT FOUND SET @id = NULL; SET _parent = @id; SET _id = -1; IF @id IS NULL THEN RETURN NULL; END IF; LOOP SELECT MIN(id) INTO @id FROM categories WHERE parent = _parent AND id > _id; 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 categories WHERE id = _parent; END LOOP; END

并在查询中使用它:

SELECT id, parent, level FROM ( SELECT hierarchy_connect_by_parent_eq_prior_id(id) AS id, @level AS level FROM ( SELECT @start_with := 0, @id := @start_with, @level := 0 ) vars, categories WHERE @id IS NOT NULL ) ho JOIN categories hi ON hi.id = ho.id

有关更多详细信息，请参见我的博客中的条目:

• > MySQL中的分层查询

I'm working with mySQL, and I'm in a situation where I need to select data from one table that matches an ID at any level in parent -> child data hierarchy in the other table.

Further more, I would like to resolve this with a well written SQL query, rather than a recursive function in my PHP code, as this feature will be used quite a bit.

I did try searching, and I have stumbled upon numerous similar problems (most of them being resolved), however none of them helped me.

To help illustrate the situation, here's my current setup

table "articles":

• article_id
• category_id
• ...

table categories

• category_id
• parent_id
• ...

I need to select all the articles from "articles" where "articles.category_id" is, let's say, 10. But also receive all the articles from all categories from the tree the "categories.category_id" 10 belongs to.

Meaning, where "10" is the parent and all of it's children, and upwards where 10 is the child and all of it's parents.

Possible without a recursive php function?

Thank you.

解决方案

This is possible to do in MySQL, but it takes a little effort. You'll have to write a function like this:

CREATE FUNCTION hierarchy_connect_by_parent_eq_prior_id(value INT) RETURNS INT NOT DETERMINISTIC READS SQL DATA BEGIN DECLARE _id INT; DECLARE _parent INT; DECLARE _next INT; DECLARE CONTINUE HANDLER FOR NOT FOUND SET @id = NULL; SET _parent = @id; SET _id = -1; IF @id IS NULL THEN RETURN NULL; END IF; LOOP SELECT MIN(id) INTO @id FROM categories WHERE parent = _parent AND id > _id; 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 categories WHERE id = _parent; END LOOP; END

and use it in a query:

SELECT id, parent, level FROM ( SELECT hierarchy_connect_by_parent_eq_prior_id(id) AS id, @level AS level FROM ( SELECT @start_with := 0, @id := @start_with, @level := 0 ) vars, categories WHERE @id IS NOT NULL ) ho JOIN categories hi ON hi.id = ho.id

See this entry in my blog for more detail:

• Hierarchical queries in MySQL