oracle connect by递归

      oracle中的select语句可以用START WITH...CONNECT BY PRIOR子句实现递归查询，connect by 是结构化查询中用到的，其基本语法是：

select ... from <TableName> 
where <Conditional-1>
start with <Conditional-2>
connect by <Conditional-3>
;

<Conditional-1>：过滤条件，用于对返回的所有记录进行过滤。
<Conditional-2>：查询结果重起始根结点的限定条件。
<Conditional-3>：连接条件

SELECT * FROM address a ;

SELECT a1.*
FROM address a1
START WITH a1.parentid IS NULL
CONNECT BY PRIOR a1.id = a1.parentid;

SELECT a1.*
FROM address a1
WHERE a1.name <> '沙井' 
START WITH a1.parentid IS NULL
CONNECT BY PRIOR a1.id = a1.parentid;

SELECT a1.*
FROM address a1
START WITH a1.id = 100101
CONNECT BY PRIOR a1.id = a1.parentid