分层表多次合并自身

Question

   CREATE TABLE b( ID         VARCHAR2(50 BYTE),
                   PARENT_ID  VARCHAR2(50 BYTE),
                   NAME       NVARCHAR2(200)
     );

https://community.oracle.com/thread/3513540？

以上链接我解释了一切

Answer 1

你不喜欢answer posted there的任何理由？说明问题答案的SQL Fiddle不是您所描述的所需结果吗？

修改：

使用SQL Fiddle Frank Kulash技术的suggested。这是我自2002年以来编写的第一个基于Oracle的查询（在9iAS上）。

SELECT  REGEXP_SUBSTR( a.PIDPath, '[^,]+', 1, 1 )    Header1,
        REGEXP_SUBSTR( a.IDPath, '[^,]+', 1, 1 )     Header2,
        REGEXP_SUBSTR( a.NamePath, '[^,]+', 1, 1 )   Header3,

        REGEXP_SUBSTR( a.PIDPath, '[^,]+', 1, 2 )    Header4,
        REGEXP_SUBSTR( a.IDPath, '[^,]+', 1, 2 )     Header5,
        REGEXP_SUBSTR( a.NamePath, '[^,]+', 1, 2 )   Header6,

        REGEXP_SUBSTR( a.PIDPath, '[^,]+', 1, 3 )    Header7,
        REGEXP_SUBSTR( a.IDPath, '[^,]+', 1, 3 )     Header8,
        REGEXP_SUBSTR( a.NamePath, '[^,]+', 1, 3 )   Header9,

        REGEXP_SUBSTR( a.PIDPath, '[^,]+', 1, 4 )    Header10,
        REGEXP_SUBSTR( a.IDPath, '[^,]+', 1, 4 )     Header11,
        REGEXP_SUBSTR( a.NamePath, '[^,]+', 1, 4 )   Header12,

        REGEXP_SUBSTR( a.PIDPath, '[^,]+', 1, 5 )    Header13,
        REGEXP_SUBSTR( a.IDPath, '[^,]+', 1, 5 )     Header14,
        REGEXP_SUBSTR( a.NamePath, '[^,]+', 1, 5 )   Header15

        --,REGEXP_SUBSTR( a.PIDPath, '[^,]+', 1, n )    
        --,REGEXP_SUBSTR( a.IDPath, '[^,]+', 1, n )     
        --,REGEXP_SUBSTR( a.NamePath, '[^,]+', 1, n )

FROM (  SELECT  LEVEL                                RootLvl,
                b.ID                                 RootID,
                SYS_CONNECT_BY_PATH( b.PARENT_ID, ',' )
                    || ','                           PIDPath,
                SYS_CONNECT_BY_PATH( b.ID, ',' )        
                    || ','                           IDPath,
                SYS_CONNECT_BY_PATH( b.NAME, ',' )                       
                    || ','                           NamePath
        FROM    t b
        START WITH b.PARENT_ID = '1'
        CONNECT BY NOCYCLE PRIOR b.ID = b.PARENT_ID ) a
ORDER BY a.RootLvl, a.RootID;

Frank Kulash指出：

  

结果集中的列数必须硬编码到查询中。您可以编写今天生成30列的内容（即，层次结构中足够10个级别），但如果您稍后更改数据以便有11个或更多级别，那么您的查询将开始失去结果。

我可能会稍后再尝试PIVOT。甲骨文很疯狂。

修改：

但足够可管理。静态PIVOT有效just fine。我无法让CROSS APPLY像我认为应该使用VALUES（MSSQL样式）一样工作，所以我已经放弃并将其替换为可通过的UNION ALL。有一些动态SQL工作的潜力，所以它实际上可以做你需要的而不需要对列进行硬编码。

;
WITH c ( RID, ID, PARENT_ID, NAME ) AS (
    SELECT  ROW_NUMBER() OVER (
            ORDER BY PARENT_ID )        RID,
            ID, PARENT_ID, NAME
    FROM    t
    UNION ALL
    SELECT  b.RID, a.ID, a.PARENT_ID, a.NAME
    FROM    t a,
            c b
    WHERE   a.ID = b.PARENT_ID
)
SELECT  p."'ID_1'"                              Header1,
        p."'PARENT_ID_1'"                       Header2,
        p."'NAME_1'"                            Header3,
        p."'ID_2'"                              Header4,
        p."'PARENT_ID_2'"                       Header5,
        p."'NAME_2'"                            Header6,
        p."'ID_3'"                              Header7,
        p."'PARENT_ID_3'"                       Header8,
        p."'NAME_3'"                            Header9,
        p."'ID_4'"                              Header10,
        p."'PARENT_ID_4'"                       Header11,
        p."'NAME_4'"                            Header12,
        p."'ID_5'"                              Header13,
        p."'PARENT_ID_5'"                       Header14,
        p."'NAME_5'"                            Header15
FROM (  SELECT  RID, 
                'ID_' || ROW_NUMBER() OVER (
                    PARTITION BY RID
                    ORDER BY ID )               KeyName,
                ID                              KeyValue
        FROM    c
        UNION ALL
        SELECT  RID, 
                'PARENT_ID_' || ROW_NUMBER() OVER (
                    PARTITION BY RID
                    ORDER BY ID )               KeyName,
                PARENT_ID                       KeyValue
        FROM    c
        UNION ALL
        SELECT  RID, 
                'NAME_' || ROW_NUMBER() OVER (
                    PARTITION BY RID
                    ORDER BY ID )               KeyName,
                CAST( NAME AS VARCHAR2( 200 ) ) KeyValue
        FROM    c ) s
PIVOT ( MAX( KeyValue ) FOR KeyName IN (
            'ID_1', 'PARENT_ID_1', 'NAME_1',
            'ID_2', 'PARENT_ID_2', 'NAME_2',
            'ID_3', 'PARENT_ID_3', 'NAME_3',
            'ID_4', 'PARENT_ID_4', 'NAME_4',
            'ID_5', 'PARENT_ID_5', 'NAME_5' ) ) p
ORDER BY p.RID;