sql 基础 四 树查询

1、从叶子节点依据id=pid的关系向上递归到跟节点。select t.*, t.rowid from indicators t start with (t.isleaf='1' and t.rid='26020')connect by prior t.pid = t.id order by t.inum从跟节点依据id=pid的关系向下递归至叶子节点.select t.*, t.rowid from indicators t start with (t.pid='0' and t.rid='26020')connect by prior t.id = t.pid order by t.inum2、decode的用法 decode(条件,值1,返回值1,值2,返回值2,...值n,返回值n,缺省值)  [类似于 switch 语句] decode(字段或字段的运算，值1，值2，值3） [如果是 值1 ，返回值2，否则返回 值3] SELECT DECODE (value, <if this value>, <return this value>) FROM table_name 统计男女人数： select sum(decode(sex,'男',1,0)),sum(decode(sex,'女',1,0)) from table_name