我如何加入同一个表并在sql中对其排序? [英] How do i join same table and sort it in sql?

问题描述

我有一张像下面的桌子-

I have table like below one -

Name      Null     Type         
--------- -------- ------------ 
ID        NOT NULL NUMBER       
Name               VARCHAR2(20) 
PARENT_ID          NUMBER  

表内容

ID        Name     PARENT_ID
--------- -------- ------------ 
1         Ramesh    null*
2         Ajay      1

我想找出最佳的SQL连接查询，在其中可以填充如下所示的结果.

I want to find out best SQL join query where I can populate the results like below.

对于每一行，我想知道ParentName而不是ID.我该怎么办?

For each row I want to know the ParentName not ID. How can I do that ?

ID        Name     ParentName
--------- -------- ------------ 
1         Ramesh    null*
2         Ajay      Ramesh

* null或空白

这不是我的要求的示例.

This is not example of the my requirement.

我已经尝试在SQL下使用左联接，但是我不确定它是否正确.

I have tried below SQL with left join but I am not sure if its the proper way.

SELECT S1.ID,S1.CRID AS PARENT_CRID,S2.CRID AS CRID  FROM DAJ_JOINS S1
left JOIN DAJ_JOINS S2
ON S1.ID=S2.PARENT_ID
order by id  asc;

推荐答案

您的查询已结束，但需要将连接子句反转为

Your query is close but the joining clause needs to be reversed as

select 
t1.ID,
t1.Name,
t2.Name as PARENT_Name
from DAJ_JOINS t1
left join DAJ_JOINS t2 on t1.PARENT_ID = t2.ID
order by t1.ID

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