Home Database Mysql Tutorial ORACLE中数据递归查询遍历sql语句

ORACLE中数据递归查询遍历sql语句

Jun 07, 2016 pm 05:45 PM
oracle sql data Inquire recursion Traverse

查询遍历,需要在将数据在基表中按照层次结构进行存储。比如一个组织机构就是这样的典型例子:

  实现语句:

 

 select column

  from table_name

  start with column=value

  connect by prior 父主键=子外键

  例1:在oracle的emp 表中,每一条记录都有一个唯一标识当前雇员的empno和标识这个雇员的经理的mgr列。如果mgr 为空,则该雇员是该机构的最顶级。现在要列出每个雇员的层次结构(从顶到底):

 

 select lpad(' ',4*(level-1))||ename name ,empno,mgr from emp

  start with mgr is null

  connect by prior empno=mgr;

  name                    empno     mgr

  --------------------                ---------      ---------

  king                      7839

  jones                 7566      7839

  scott             7788      7566

  adams        7876     7788

  ford              7902      7566

  smith         7369      7902

  blake                 7698      7839

  allen             7499      7698

  ward              7521      7698

  martin            7654      7698

  turner            7844      7698

  james             7900     7698

  clark                 7782      7839

  miller            7934      7782

  14 rows selected.

  sql>

  

从查询结果中可以看出,由于jones、blake、clark的上司是king,所以jones等mgr(经理编号)=king的empno号,即king的直接下级是jones、blake、clark,因为他们的mgr与king的empno一样。

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