[转自] http://blog.csdn.net/rfb0204421/article/details/7675911
注意:与max,min的区别,虽然也可以实现,但只是针对数字字段.
1、初始化原始数据:
create table test (id number(2), name varchar2(10), salary number(6,2)); insert into test values (1,'Tom',120); insert into test values (2,'Ellen',240); insert into test values (2,'Joe',80); insert into test values (3,'Andy',300); insert into test values (3,'Kary',500); insert into test values (3,'Erick',1300); insert into test values (3,'Hou',40); insert into test values (3,'Mary',200); insert into test values (3,'Secooler',800); commit; select * from test order by ID,name; ID NAME SALARY --- ---------- -------- 1 Tom 120.00 2 Ellen 240.00 2 Joe 80.00 3 Andy 300.00 3 Erick 1300.00 3 Hou 40.00 3 Kary 500.00 3 Mary 200.00 3 Secooler 800.00
2、LAST_VALUE分析函数的简单用法
(1)在TEST表中添加一列,标识每一个数据分区中薪水最高的人名。
select ID, name, salary, LAST_VALUE(name) OVER (partition by ID order by salary ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) as highest_sal_name from test order by ID, name; ID NAME SALARY HIGHEST_SAL_NAME --- ---------- -------- ---------------- 1 Tom 120.00 Tom 2 Ellen 240.00 Ellen 2 Joe 80.00 Ellen 3 Andy 300.00 Erick 3 Erick 1300.00 Erick 3 Hou 40.00 Erick 3 Kary 500.00 Erick 3 Mary 200.00 Erick 3 Secooler 800.00 Erick
注意其中“ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING”的使用,若省略效果如下。
select ID, name, salary, LAST_VALUE(name) OVER (partition by ID order by salary) as highest_sal_name from test order by ID,name; ID NAME SALARY HIGHEST_SAL_NAME --- ---------- -------- ---------------- 1 Tom 120.00 Tom 2 Ellen 240.00 Ellen 2 Joe 80.00 Joe 3 Andy 300.00 Andy 3 Erick 1300.00 Erick 3 Hou 40.00 Hou 3 Kary 500.00 Kary 3 Mary 200.00 Mary 3 Secooler 800.00 Secooler
显然这不是我们想要的效果:(,这是为什么呢~~~?给您一次思考和回答的机会。
如果对UNBOUNDED PRECEDING和UNBOUNDED FOLLOWING不熟悉,请参考Oracle官方文档“windowing_clause”http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/functions001.htm#i97640。
在TEST表中添加一列,标识每一个数据分区中薪水最高的薪水值。
col highest_sal_name for 9999 select ID, name, salary, LAST_VALUE(SALARY) OVER (partition by ID order by salary ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) as highest_sal_name from test order by ID, name; ID NAME SALARY HIGHEST_SAL_NAME --- ---------- -------- ---------------- 1 Tom 120.00 120 2 Ellen 240.00 240 2 Joe 80.00 240 3 Andy 300.00 1300 3 Erick 1300.00 1300 3 Hou 40.00 1300 3 Kary 500.00 1300 3 Mary 200.00 1300 3 Secooler 800.00 1300
3、与之相对应的是FIRST_VALUE函数
select ID, name, salary, FIRST_VALUE(name) OVER (partition by ID order by salary ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) as highest_sal_name from test order by ID, name; ID NAME SALARY HIGHEST_SAL_NAME --- ---------- -------- ---------------- 1 Tom 120.00 Tom 2 Ellen 240.00 Joe 2 Joe 80.00 Joe 3 Andy 300.00 Hou 3 Erick 1300.00 Hou 3 Hou 40.00 Hou 3 Kary 500.00 Hou 3 Mary 200.00 Hou 3 Secooler 800.00 Hou
select ID, name, salary, FIRST_VALUE(SALARY) OVER (partition by ID order by salary ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) as highest_sal_name from test order by ID, name; ID NAME SALARY HIGHEST_SAL_NAME --- ---------- -------- ---------------- 1 Tom 120.00 120 2 Ellen 240.00 80 2 Joe 80.00 80 3 Andy 300.00 40 3 Erick 1300.00 40 3 Hou 40.00 40 3 Kary 500.00 40 3 Mary 200.00 40 3 Secooler 800.00 40