MySql 从同一个表中检索数据答案

【问题标题】：MySql Retrieve data from same tableMySql 从同一个表中检索数据
【发布时间】：2010-06-01 15:25:17
【问题描述】：

我有一张表，其中包含*菜单的 id、name、parentId 及其子菜单，例如：

--------------------------------------
    id    |    name    |    parentId 
--------------------------------------
    1     |    Color   |       0
--------------------------------------
    2     |    Flower  |       0
--------------------------------------
    3     |    Red     |       1
--------------------------------------
    4     |    pink    |       1
--------------------------------------
    5     |    Rose    |       2
--------------------------------------
    6     |    Lily    |       2
--------------------------------------

我想获取这些记录，结果数组必须是这样的

---------------------------------------------------------------
    id    |    Pname    |    parentId  |  child    |   childId
---------------------------------------------------------------
    1     |    Color   |       1      |   Red     |    3
---------------------------------------------------------------
    2     |    Color   |       1      |   Pink    |    4
---------------------------------------------------------------
    3     |    Flower  |       2      |   Rose    |    5
---------------------------------------------------------------
    4     |    Flower  |       2      |   Lily    |    6
---------------------------------------------------------------

我的查询是这样的：

SELECT name AS Pname FROM myTbl WHERE id = (SELECT parentId FROM myTbl WHERE parentId = 1 )

但是 mysql 说 #1242 - 子查询返回超过 1 行

谁能解决？谢谢..

【问题讨论】：

标签： mysql mysql-error-1242

【解决方案1】：

SELECT t1.id, t1.name AS Pname, 
    t2.parentId, t2.name as child, t2.id as childId
FROM myTbl t1
INNER JOIN myTbl t2 on t1.id = t2.parentId

【讨论】：

稍作改动。SELECT t1.name as 'Parent', t1.id as 'Parent Id', t2.name as 'Child', t2.id as 'Child Id' FROM mytable t1 INNER JOIN mytable t2 ON t1.id = t2.parentId

【解决方案2】：

出现问题是因为您的子查询返回多行。解决方案是确保子查询只返回一行，或者确保它返回更多并不重要

但这些并不能真正为您提供表格建议的结果

SELECT name AS Pname 
 FROM myTbl 
WHERE id = ( SELECT DISTINCT parentId 
               FROM myTbl 
              WHERE parentId = 1 
           )

或

SELECT name AS Pname 
 FROM myTbl 
WHERE id IN ( SELECT DISTINCT parentId 
                FROM myTbl 
               WHERE parentId = 1 
            )

【讨论】：