Recursive query of mysql and oracle

 

There are many ways to implement recursive query in Oracle

Method 1: Recursion through the with clause

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1. withtemp(id,parentid) as (   
2.  select id,parentid  
3.  from t  
4.  where t.id = '1'  
5.  union all   
6.  select t.id, t.parentid  
7.  fromtemp, t   
8.  wheretemp.parentid = t.id)   

The recursive with clause in the with clause achieves the effect of recursive query

Method 2: Implemented through connect by provided by oracle

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1. SELECT id, parentid  
2. FROM t  
3. CONNECTBY id = PRIOR parentid   
4. START WITH id = '1';  

Prior means downward recursion in front of parentid, and upward recursion in front of id

 

Implementation of recursion in MySQL :

MySQL does not provide the syntax of connect by, nor the with clause, so how to do it? We define a function implementation

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1. delimiter //  
2. DROPFUNCTION IF EXISTS queryChildren;   
3. CREATEFUNCTION `queryChildren` (areaId INT)   
4. RETURNSVARCHAR(4000)   
5. BEGIN  
6. DECLARE sTemp VARCHAR(4000);  
7. DECLARE sTempChd VARCHAR(4000);  
8.   
9. SET sTemp = '$';  
10. SET sTempChd = cast(areaId aschar);   
11.   
12. WHILE sTempChd isnotNULL DO    
13. SET sTemp = CONCAT(sTemp,',',sTempChd);  
14. SELECT group_concat(id) INTO sTempChd FROM t_areainfo where FIND_IN_SET(parentId,sTempChd)>0;  
15. END WHILE;  
16. return sTemp;  
17. END;  
18. //  

Use this function in the sql statement

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1. select * from t_areainfo where find_in_set(id,queryChildrenAreaInfo(1)); 
   

 

 

 

This article comes from: http://blog.csdn.net/yangnianbing110/article/details/36664799