将树关系节点名称拼成字符串sql

树自关联表sql，将关系节点名称拼成字符串：

关键字prior ：影响最后拼写成的path字符串，放在t.id前，则拼成的串从根->叶。放在t.parentid前，则拼成从叶->根
1.从根往下查

select sys_connect_by_path(t.name, '>>') path form mytable t
 where 1 = 1
 start with t.parentid = 'root'
connect by prior t.id = t.prarentid

2.从子往根查

select sys_connect_by_path(t.name, '>>') path form mytable t
 where 1 = 1
 start with t.isleaf = true
connect by prior t.id = t.prarentid