Oracle树查询

1、Oracle函数 sys_connect_by_path

语法： select sys_connect_by_path(column_name,'connect_symbo链接标志l')  from table 
        　　start with ... connect by prior

写法：connect by prior column1 = column2 或者 connect by  column2 = prior column1 写法都可以，

主要看prior写在谁的前面，prior写在谁的前面谁就作为父级值（参照值）

 例：

select sys_connect_by_path(ghdm,'-') from gh_ghdm start with ghdm = 22333 connect by prior ghdm =  sjghdm

select sys_connect_by_path(ghdm,'-') from gh_ghdm start with ghdm = 22333 connect by  ghdm = prior sjghdm

 相关链接https://www.cnblogs.com/supermandy/p/7873233.html