oracle 中start with 的用法

在重新开发已经有过的一个项目时，参考原本的sql，在一个存储过程中有用到 start with connect by,从网络找到下面资料。

Oracle 提供了start with connect by 语法结构可以实现递归查询。

from
test;

 DAY_NUMBER
MSISDN
-------------------- ---------- --------------------
200803                        1
13800
200803                        3
13800
200803                        2
13800
200803                        2
13801
200803                        4
13804
200803                        5
13804
200803                        7
13804
200803                        8
13804
200803                        6
13802
200803                        6
13801
200803                        7
13801
200803                        8
13801

SQL>
SQL> select * from test
  2       start
with day_number=1
  3       connect
by  prior
day_number=day_number-1 and prior msisdn= msisdn
  4      ;

 DAY_NUMBER
MSISDN
-------------------- ---------- --------------------
200803                        1
13800
200803                        2
13800
200803                        3
13800

connect
by 语法结构
 如上面说看到的
例子， 其语法结构为  start
with condition  connect
by  condition
（含 prior 关键字)
start with conditon 给出的seed 数据的范围, connect by  后面给出了递归查询的条件,prior
关键字表示父数据，prior 条件表示子数据需要满足父数据的什么条件。

start with day_number=1
     connect
by  prior
day_number=day_number-1 and prior msisdn= msisdn