怎么能做到oracle批量修改数据？？？？？

Question

现在有一张表，数据量有十万，有一个字段是空的，现在要按数据量比例给这个字段设置三个不同的值，比如百分之三十的数据设置成1，百分之三十设置成2，剩下的百分之四十设置成3。比例无所谓不固定。
有没有大神教一下啊。。。

Answer 1

--建表
create table t (a number);
--插入两条测试数据
insert into t values(0);
insert into t values(0);
--测试语句
select case
when (select count(1) from t where t.a = 0) =
(select count(1) from t) then
'01'
when (select count(1) from t where t.a = 0) <>
(select count(1) from t) then
'02'
when (select count(1) from t where t.a = 2) <>
(select count(1) from t) then
'03'
when (select count(1) from t where t.a = 2) = 0 then
'04'
else
null
end as b
from dual;

参考：http://bbs.csdn.net/topics/330059135