Oracle数据库表嵌套查询问题

目前有两张表

type

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ID| Name

--------------------

1 | 林地

--------------------

2 | 耕地

--------------------

ground

ID|oldtype |nowtype

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1 | 1 | 2

----------------------------------------

2 | 2 | 1

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目标是生成以下视图

sv_GroundType

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ID|oldtype| nowtype

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1 | 林地 | 耕地

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2 | 耕地 | 林地

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语句：

create or replace view sv_GroundType as
select oldid ID,oldname oldtype,nowname nowtype
from
(select a.id oldid,b.name oldtype from ground a,type b where a.oldtype=b.id),
(select c.id newid,d.name nowname from ground c,type d where a.nowtype=c.id)
where oldid = newid

不知道如何精确描述这样的问题，先这样记下来吧，希望能对看到的人有所帮助。

更高级点的写法：

SELECT
Type_1.TypeName,
Type.TypeName,
Ground.ID,
Ground.LYR_SEQ,
Layer.LayerName,
FROM
Layer
RIGHT JOIN
(((Ground
INNER JOIN
Ground AS Ground_1
ON Ground.ID = Ground_1.ID)
INNER JOIN Type
ON Ground.NowType = Type.TypeID)
INNER JOIN Type AS Type_1
ON Ground_1.OldType = Type_1.TypeID)
ON Layer.LYR_SEQ = Ground.LYR_SEQ;