自參照表的SQL查詢來行

Question

我有這樣的Oracle 11g查詢：

SELECT RPAD(' ', 2 * (T.ID_LEVEL - 1)) || T.IDE IDE, T.ID_LEVEL, T.CODE, T.FK_IDE 
FROM TEST_DYNAMIC T 
START WITH T.FK_IDE = 0 
CONNECT BY NOCYCLE PRIOR T.IDE = T.FK_IDE 
ORDER BY T.IDE,T.FK_IDE; 

返回此數據：

IDE |IDE_LEVEL |CODE |FK_IDE | 
-----|-----------|------|--------| 
1 |   1|A01 |  0| 
2 |   2|A01 |  1| 
    3 |   3|A01 |  2| 
    4|   4|A01 |  3| 
5 |   2|A02 |  1| 
6 |   2|A03 |  1| 
    7 |   3|A01 |  6| 
8 |   1|A02 |  0| 

正如你所看到的，是從自我refrencing表得到的數據，其中IDE_LEVEL列是包含此值（1，2，3，4）作爲PK的主表的外鍵，而IDE列是來自TEST_DYNAMIC表的自動增量PK。

有一種方法以該結果轉換爲這一個？：

IDE |CODE_LEVEL1 |CODE_LEVEL2 |CODE_LEVEL3 |CODE_LEVEL4 | 
-----|-------------|-------------|-------------|-------------| 
1 |A01   |A01   |A01   |A01   | 
1 |A01   |A02   |NULL   |NULL   | 
1 |A01   |A03   |A01   |NULL   | 
8 |A02   |NULL   |NULL   |NULL   | 

在預期的結果如上所述，IDE列被示出對應於在FK_COLUMN三個ocurrences關鍵1三次，和第一個結果集中鍵8的一次（這一個沒有子元素，因此必須顯示在結果集中）。

任何幫助將不勝感激。

Answer 1

起初我沒有得到這個問題。你不需要PIVOT，你需要在不同的列中顯示每個分支的路徑。無論如何，根據級別的數量，你可能需要一些動態的sql

with test_dynamic as (
select 1 ide, 1 id_level, 'A01' code, 0 fk_ide from dual 
union all select 2, 2, 'A01', 1 from dual 
union all select 3, 3, 'A01', 2 from dual 
union all select 4, 4, 'A01', 3 from dual 
union all select 5, 2, 'A02', 1 from dual 
union all select 6, 2, 'A03', 1 from dual 
union all select 7, 3, 'A01', 6 from dual 
union all select 8, 1, 'A02', 0 from dual 
), 
tree as (
select code, level lvl, sys_connect_by_path(code, '/') path, connect_by_isleaf lf, connect_by_root(ide) root_ide 
from test_dynamic t 
start with t.fk_ide = 0 
connect by nocycle prior t.ide = t.fk_ide 
) 
select root_ide, path, 
     regexp_substr(path, '[^/]+', 1, 1), 
     regexp_substr(path, '[^/]+', 1, 2), 
     regexp_substr(path, '[^/]+', 1, 3), 
     regexp_substr(path, '[^/]+', 1, 4) 
from tree where lf = 1; 

Answer 2

如果級別的數量是動態的，那麼無論如何您都需要使用動態SQL來創建具有動態列的查詢。

至少有2種方法如何創建這樣一個查詢：

1）甲骨文與PIVOT（因爲11克我想）

with test_dynamic as (
select 1 ide, 1 id_level, 'A01' code, 0 fk_ide from dual 
union all select 2, 2, 'A01', 1 from dual 
union all select 3, 3, 'A01', 2 from dual 
union all select 4, 4, 'A01', 3 from dual 
union all select 5, 2, 'A02', 1 from dual 
union all select 6, 2, 'A03', 1 from dual 
union all select 7, 3, 'A01', 6 from dual 
union all select 8, 1, 'A02', 0 from dual 
), 
tree as (
select level lvl, t.ide, t.code 
from test_dynamic t 
start with t.fk_ide = 0 
connect by nocycle prior t.ide = t.fk_ide 
), 
pivot_data as (
select * from tree pivot xml (max(code) lvl_code for lvl in (select distinct lvl from tree)) 
) 
select ide, 
     extractvalue(lvl_xml,'/PivotSet/item[1]/column[2]') code_level1, 
     extractvalue(lvl_xml,'/PivotSet/item[2]/column[2]') code_level2, 
     extractvalue(lvl_xml,'/PivotSet/item[3]/column[2]') code_level3, 
     extractvalue(lvl_xml,'/PivotSet/item[4]/column[2]') code_level4 
from pivot_data t order by 1; 

（人們說，extractValue一起有可能成爲過時的和推薦使用XMLTABLE，但我從來沒有與這個工作）

2）的Oracle DECODE

with test_dynamic as (
select 1 ide, 1 id_level, 'A01' code, 0 fk_ide from dual 
union all select 2, 2, 'A01', 1 from dual 
union all select 3, 3, 'A01', 2 from dual 
union all select 4, 4, 'A01', 3 from dual 
union all select 5, 2, 'A02', 1 from dual 
union all select 6, 2, 'A03', 1 from dual 
union all select 7, 3, 'A01', 6 from dual 
union all select 8, 1, 'A02', 0 from dual 
), 
tree as (
select level lvl, t.ide, t.code 
from test_dynamic t 
start with t.fk_ide = 0 
connect by nocycle prior t.ide = t.fk_ide 
) 
select ide, 
     max(decode(lvl, 1, code, null)) code_level1, 
     max(decode(lvl, 2, code, null)) code_level2, 
     max(decode(lvl, 3, code, null)) code_level3, 
     max(decode(lvl, 4, code, null)) code_level4 
from tree group by ide order by 1;