按特殊顺序对表记录进行排序

Question

我有桌子:

+----+--------+----------+
| id | doc_id | next_req | 
+----+--------+----------+
|  1 |    1   |     4    | 
|  2 |    1   |     3    | 
|  3 |    1   |     0    | 
|  4 |    1   |     2    | 
+----+--------+----------+

id - auto incerement主键.

nex_req - 表示记录的顺序.(next_req = 记录的id)

如何构建SQL查询以此顺序获取记录:

+----+--------+----------+
| id | doc_id | next_req | 
+----+--------+----------+
|  1 |    1   |     4    | 
|  4 |    1   |     2    | 
|  2 |    1   |     3    | 
|  3 |    1   |     0    | 
+----+--------+----------+

解释:

record1 with id=1 and next_req=4 means: next must be record4 with id=4 and next_req=2
record4 with id=5 and next_req=2 means: next must be record2 with id=2 and next_req=3 
record2 with id=2 and next_req=3 means: next must be record3 with id=1 and next_req=0 
record3 with id=3 and next_req=0: means that this is a last record 

我需要在表格中存储记录顺序.这对我来说很重要.

Answer 1

我能够为您提供 Oracle 中的解决方案，

select id,doc_id,next_req from table2 
start with id = 
(select id from table2 where rowid=(select min(rowid) from table2))
connect by prior next_req=id

小提琴演示