遞歸SQL查詢來識別

Question

請參閱下面的DDL：

CREATE TABLE #MasterChild (MasterID decimal(25,0), ChildID decimal(25,0), ChildCreTime datetime) 
insert into #MasterChild values (150021032000000173536533,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173571072,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173573651,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173574917,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173582487,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173604342,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173931636,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173935066,150021032000000173946207,'2016-04-22 13:27:30.483') 
insert into #MasterChild values (150021032000000173946207,150021032000000173952172,'2016-04-22 13:38:32.747') 
insert into #MasterChild values (150021032000000173946207,150021032000000173954415,'2016-04-22 13:43:28.120') 
insert into #MasterChild values (150021032000000173536533,150021032000000173954321,'2016-04-22 13:43:28.120') 
insert into #MasterChild values (150021032000000173954321,150021032000000173954319,'2016-04-22 13:43:28.120') 

和下面的SQL：

with GetAllMerges 
as 
(
select masterid,childid from #MasterChild where masterid=150021032000000173571072 and childid=150021032000000173946207 
union all 
select #MasterChild.masterid,#MasterChild.childid from #MasterChild inner join GetAllMerges 
on 
#MasterChild.childid=GetAllMerges.masterid 
or (#MasterChild.childid=GetAllMerges.childid and #MasterChild.masterid<>GetAllMerges.masterid) 
) 
select distinct masterid,childid from GetAllMerges 

我看到下面的錯誤：

Msg 530, Level 16, State 1, Line 1 
The statement terminated. The maximum recursion 100 has been exhausted before statement completion. 

這是爲什麼？我試圖展示所有關聯的孩子和主人。例如，如果主人1連接到孩子2，並且孩子2連接到主人3，並且主人3連接到孩子4並且孩子4連接到主人5，則連接人物1-5（所有孩子和主人都是人）。

Answer 1

遞歸CTE的，你在這裏試圖做的暗示MAXRECURSION之前他們錯誤了。

您可以使用OPTION (MAXRECURSION n)指定想要的遞歸次數，其中n是介於0和32767之間的數字，其中0基本上表示無論需要多長時間才運行到競爭。

我不會告知你的情況

您的CTE不會出現有終止爲它的遞歸元素

An incorrectly composed recursive CTE may cause an infinite loop. For example, if the recursive member query definition returns the same values for both the parent and child columns, an infinite loop is created. To prevent an infinite loop, you can limit the number of recursion levels allowed for a particular statement by using the MAXRECURSION hint and a value between 0 and 32,767 in the OPTION clause of the INSERT, UPDATE, DELETE, or SELECT statement. This lets you control the execution of the statement until you resolve the code problem that is creating the loop. The server-wide default is 100. When 0 is specified, no limit is applied. Only one MAXRECURSION value can be specified per statement.

（強調）

重在更改MAXRECURSION設置之前，首先正確終止遞歸CTE，然後編寫查詢。

Answer 2

讓我看看，如果我理解你的方法：

你寫了（GetAllMerges），以顯示你想要的數據，裏面的功能回過頭來參考一下它遞歸？

==>＃MasterChild.childid = GetAllMerges.masterid < ===

我覺得你只是建立一個無限循環。

我不知道爲什麼你不只是使用一段時間或做一段時間來通過鏈接的鍵？

此外，當表名稱很長時，您可以並應該使用別名。

Answer 3

您應該切換childID的和parentId的在你的「內部聯接」這樣的：

試試吧

with GetAllMerges 
as 
(
select masterid,childid,1 AS RecLevel 
from #MasterChild 
where masterid=150021032000000173571072 and childid=150021032000000173946207 
union all 
select #MasterChild.masterid,#MasterChild.childid,GetAllMerges.RecLevel + 1 
from #MasterChild 
inner join GetAllMerges on #MasterChild.masterid=GetAllMerges.ChildID 
--or (#MasterChild.childid=GetAllMerges.childid and #MasterChild.masterid<>GetAllMerges.masterid) 
) 
select distinct masterid,childid from GetAllMerges 

我評論的or (#MasterChild...了，因爲這會產生錯誤...請描述一下你正努力實現...