我有一个MySQL表,如下所示:

id name parent_id
19 category1 0
20 category2 19
21 category3 20
22 category4 21
... ... ...

现在,我想有一个单一的MySQL查询,我只是提供id[例如说id=19],然后我应该得到它的所有子id[即结果应该有id '20,21,22']....

孩子们的等级尚不清楚;它可以变化....

我知道如何使用for循环…但是如何使用一个MySQL查询来实现相同的功能呢?


当前回答

我能想到的最好方法是

使用沿袭存储\排序\跟踪树。这已经足够了,而且阅读速度比其他任何方法都要快数千倍。 它还允许即使DB将改变也保持该模式(因为任何DB将允许使用该模式) 使用为特定ID确定谱系的函数。 您可以随心所欲地使用它(在选择中,或在CUD操作中,甚至按作业)。

谱系方法描述。可以在任何地方找到,例如 这里或者这里。 至于功能,这就是我的灵感所在。

在最后-得到或多或少简单,相对快速,简单的解决方案。

函数的身体

-- --------------------------------------------------------------------------------
-- Routine DDL
-- Note: comments before and after the routine body will not be stored by the server
-- --------------------------------------------------------------------------------
DELIMITER $$

CREATE DEFINER=`root`@`localhost` FUNCTION `get_lineage`(the_id INT) RETURNS text CHARSET utf8
    READS SQL DATA
BEGIN

 DECLARE v_rec INT DEFAULT 0;

 DECLARE done INT DEFAULT FALSE;
 DECLARE v_res text DEFAULT '';
 DECLARE v_papa int;
 DECLARE v_papa_papa int DEFAULT -1;
 DECLARE csr CURSOR FOR 
  select _id,parent_id -- @n:=@n+1 as rownum,T1.* 
  from 
    (SELECT @r AS _id,
        (SELECT @r := table_parent_id FROM table WHERE table_id = _id) AS parent_id,
        @l := @l + 1 AS lvl
    FROM
        (SELECT @r := the_id, @l := 0,@n:=0) vars,
        table m
    WHERE @r <> 0
    ) T1
    where T1.parent_id is not null
 ORDER BY T1.lvl DESC;
 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    open csr;
    read_loop: LOOP
    fetch csr into v_papa,v_papa_papa;
        SET v_rec = v_rec+1;
        IF done THEN
            LEAVE read_loop;
        END IF;
        -- add first
        IF v_rec = 1 THEN
            SET v_res = v_papa_papa;
        END IF;
        SET v_res = CONCAT(v_res,'-',v_papa);
    END LOOP;
    close csr;
    return v_res;
END

然后你就

select get_lineage(the_id)

希望它能帮助到一些人:)

其他回答

从博客管理分层数据在MySQL

表结构

+-------------+----------------------+--------+
| category_id | name                 | parent |
+-------------+----------------------+--------+
|           1 | ELECTRONICS          |   NULL |
|           2 | TELEVISIONS          |      1 |
|           3 | TUBE                 |      2 |
|           4 | LCD                  |      2 |
|           5 | PLASMA               |      2 |
|           6 | PORTABLE ELECTRONICS |      1 |
|           7 | MP3 PLAYERS          |      6 |
|           8 | FLASH                |      7 |
|           9 | CD PLAYERS           |      6 |
|          10 | 2 WAY RADIOS         |      6 |
+-------------+----------------------+--------+

查询:

SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3, t4.name as lev4
FROM category AS t1
LEFT JOIN category AS t2 ON t2.parent = t1.category_id
LEFT JOIN category AS t3 ON t3.parent = t2.category_id
LEFT JOIN category AS t4 ON t4.parent = t3.category_id
WHERE t1.name = 'ELECTRONICS';

输出

+-------------+----------------------+--------------+-------+
| lev1        | lev2                 | lev3         | lev4  |
+-------------+----------------------+--------------+-------+
| ELECTRONICS | TELEVISIONS          | TUBE         | NULL  |
| ELECTRONICS | TELEVISIONS          | LCD          | NULL  |
| ELECTRONICS | TELEVISIONS          | PLASMA       | NULL  |
| ELECTRONICS | PORTABLE ELECTRONICS | MP3 PLAYERS  | FLASH |
| ELECTRONICS | PORTABLE ELECTRONICS | CD PLAYERS   | NULL  |
| ELECTRONICS | PORTABLE ELECTRONICS | 2 WAY RADIOS | NULL  |
+-------------+----------------------+--------------+-------+

大多数用户都曾经在SQL数据库中处理过层次数据,毫无疑问,他们知道层次数据的管理不是关系数据库的目的。关系数据库的表不是分层的(像XML一样),而只是一个平面列表。层次数据具有亲子关系,在关系数据库表中不能自然地表示这种关系。 阅读更多

更多细节请参考博客。

编辑:

select @pv:=category_id as category_id, name, parent from category
join
(select @pv:=19)tmp
where parent=@pv

输出:

category_id name    parent
19  category1   0
20  category2   19
21  category3   20
22  category4   21

参考:如何在Mysql中做递归SELECT查询?

这对我有用,希望这对你也有用。它会给你一个记录集根到子为任何特定的菜单。根据您的需求更改字段名称。

SET @id:= '22';

SELECT Menu_Name, (@id:=Sub_Menu_ID ) as Sub_Menu_ID, Menu_ID 
FROM 
    ( SELECT Menu_ID, Menu_Name, Sub_Menu_ID 
      FROM menu 
      ORDER BY Sub_Menu_ID DESC
    ) AS aux_table 
    WHERE Menu_ID = @id
     ORDER BY Sub_Menu_ID;

这是一个有点棘手的问题,检查一下它是否适合你

select a.id,if(a.parent = 0,@varw:=concat(a.id,','),@varw:=concat(a.id,',',@varw)) as list from (select * from recursivejoin order by if(parent=0,id,parent) asc) a left join recursivejoin b on (a.id = b.parent),(select @varw:='') as c  having list like '%19,%';

SQL小提琴链接http://www.sqlfiddle.com/#!2 / e3cdf / 2

用字段名和表名替换。

试试这些:

表定义:

DROP TABLE IF EXISTS category;
CREATE TABLE category (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(20),
    parent_id INT,
    CONSTRAINT fk_category_parent FOREIGN KEY (parent_id)
    REFERENCES category (id)
) engine=innodb;

实验行:

INSERT INTO category VALUES
(19, 'category1', NULL),
(20, 'category2', 19),
(21, 'category3', 20),
(22, 'category4', 21),
(23, 'categoryA', 19),
(24, 'categoryB', 23),
(25, 'categoryC', 23),
(26, 'categoryD', 24);

存储过程:

DROP PROCEDURE IF EXISTS getpath;
DELIMITER $$
CREATE PROCEDURE getpath(IN cat_id INT, OUT path TEXT)
BEGIN
    DECLARE catname VARCHAR(20);
    DECLARE temppath TEXT;
    DECLARE tempparent INT;
    SET max_sp_recursion_depth = 255;
    SELECT name, parent_id FROM category WHERE id=cat_id INTO catname, tempparent;
    IF tempparent IS NULL
    THEN
        SET path = catname;
    ELSE
        CALL getpath(tempparent, temppath);
        SET path = CONCAT(temppath, '/', catname);
    END IF;
END$$
DELIMITER ;

存储过程的包装器函数:

DROP FUNCTION IF EXISTS getpath;
DELIMITER $$
CREATE FUNCTION getpath(cat_id INT) RETURNS TEXT DETERMINISTIC
BEGIN
    DECLARE res TEXT;
    CALL getpath(cat_id, res);
    RETURN res;
END$$
DELIMITER ;

选择的例子:

SELECT id, name, getpath(id) AS path FROM category;

输出:

+----+-----------+-----------------------------------------+
| id | name      | path                                    |
+----+-----------+-----------------------------------------+
| 19 | category1 | category1                               |
| 20 | category2 | category1/category2                     |
| 21 | category3 | category1/category2/category3           |
| 22 | category4 | category1/category2/category3/category4 |
| 23 | categoryA | category1/categoryA                     |
| 24 | categoryB | category1/categoryA/categoryB           |
| 25 | categoryC | category1/categoryA/categoryC           |
| 26 | categoryD | category1/categoryA/categoryB/categoryD |
+----+-----------+-----------------------------------------+

过滤指定路径的行:

SELECT id, name, getpath(id) AS path FROM category HAVING path LIKE 'category1/category2%';

输出:

+----+-----------+-----------------------------------------+
| id | name      | path                                    |
+----+-----------+-----------------------------------------+
| 20 | category2 | category1/category2                     |
| 21 | category3 | category1/category2/category3           |
| 22 | category4 | category1/category2/category3/category4 |
+----+-----------+-----------------------------------------+

我能想到的最好方法是

使用沿袭存储\排序\跟踪树。这已经足够了,而且阅读速度比其他任何方法都要快数千倍。 它还允许即使DB将改变也保持该模式(因为任何DB将允许使用该模式) 使用为特定ID确定谱系的函数。 您可以随心所欲地使用它(在选择中,或在CUD操作中,甚至按作业)。

谱系方法描述。可以在任何地方找到,例如 这里或者这里。 至于功能,这就是我的灵感所在。

在最后-得到或多或少简单,相对快速,简单的解决方案。

函数的身体

-- --------------------------------------------------------------------------------
-- Routine DDL
-- Note: comments before and after the routine body will not be stored by the server
-- --------------------------------------------------------------------------------
DELIMITER $$

CREATE DEFINER=`root`@`localhost` FUNCTION `get_lineage`(the_id INT) RETURNS text CHARSET utf8
    READS SQL DATA
BEGIN

 DECLARE v_rec INT DEFAULT 0;

 DECLARE done INT DEFAULT FALSE;
 DECLARE v_res text DEFAULT '';
 DECLARE v_papa int;
 DECLARE v_papa_papa int DEFAULT -1;
 DECLARE csr CURSOR FOR 
  select _id,parent_id -- @n:=@n+1 as rownum,T1.* 
  from 
    (SELECT @r AS _id,
        (SELECT @r := table_parent_id FROM table WHERE table_id = _id) AS parent_id,
        @l := @l + 1 AS lvl
    FROM
        (SELECT @r := the_id, @l := 0,@n:=0) vars,
        table m
    WHERE @r <> 0
    ) T1
    where T1.parent_id is not null
 ORDER BY T1.lvl DESC;
 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    open csr;
    read_loop: LOOP
    fetch csr into v_papa,v_papa_papa;
        SET v_rec = v_rec+1;
        IF done THEN
            LEAVE read_loop;
        END IF;
        -- add first
        IF v_rec = 1 THEN
            SET v_res = v_papa_papa;
        END IF;
        SET v_res = CONCAT(v_res,'-',v_papa);
    END LOOP;
    close csr;
    return v_res;
END

然后你就

select get_lineage(the_id)

希望它能帮助到一些人:)