oracle keep(first/last)
先看一段ORACLE官方文档
http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96520/analysis.htm#25806:
FIRST/LAST Functions
The FIRST/LAST aggregate functions allow you to return the result of an aggregate applied over a set of rows that rank as the first or last with respect to a given order specification. FIRST/LAST lets you order on column A but return an result of an aggregate applied on column B. This is valuable because it avoids the need for a self-join or subquery, thus improving performance. These functions begin with a tiebreaker function, which is a regular aggregate function (MIN, MAX, SUM, AVG, COUNT, VARIANCE, STDDEV) that produces the return value. The tiebreaker function is performed on the set rows (1 or more rows) that rank as first or last respect to the order specification to return a single value.
To specify the ordering used within each group, the FIRST/LAST functions add a new clause starting with the word KEEP.
大意是说FIRST/LAST函数按照某个字段排序后取得第一行或者最后一行,FIRST/LAST聚集函数可以按A列排序,B列聚集,避免了自连接和子查询.分组聚合函数(min,max....)位于FIRST/LAST函数之前产生多行结果集,并且按照排序返回FIRST/LAST单个值.
要指定在每个组的顺序，FIRST/LAST函数之前加上以关键字KEEP开始即可
FIRST/LAST Syntax
These functions have the following syntax:
aggregate_function KEEP
( DENSE_RANK LAST ORDER BY
expr [ DESC | ASC ] [NULLS { FIRST | LAST }]
[, expr [ DESC | ASC ] [NULLS { FIRST | LAST }]]...)
[OVER query_partitioning_clause]
Note that the ORDER BY clause can take multiple expressions.请注意在ORDER BY子句可以采取多种表现形式
Returns the row ranked first using DENSE_RANK
2种取值：
DENSE_RANK FIRST
DENSE_RANK LAST
在keep (DENSE_RANK first ORDER BY sl) 结果集中再取max、min的例子。
例子如下:oracle分析函数中，keep and over的区别
公司部门中入厂时间最早的员工的薪水最小的是多少
SQL>SELECT deptno,ename,empno,sal,
MIN(sal) KEEP (dense_rank FIRST ORDER BY hiredate) over (PARTITION
相关文档：
经验：
alter system set log_archive_dest=’D:\oracle\archivelog’ scope=spfile;
alter system set log_archive_start=true scope=spfile;
之后，
create pfile from spfile
可验证加上没
一、查看数据库运行模式
可以用超级用户（INTERNAL）在SQLPLUS中使用命令ARCHIVE LOG LIST查看
......
1.创建过程
与其它的数据库系统一样，Oracle的存储过程是用PL/SQL语言编写的能完成一定处理功能的存储在数据库字典中的程序。
语法:
create [or replace] procedure procedure_name
[ (argment [ { in| in out }] type,
argment [ { in | out | in out } ] type
{ is | as }
<类型 ......
推荐crs版本高于db版本
If you also plan to apply this patch to Oracle Clusterware,
ensure that you apply the patch to Oracle Clusterware before
applying it to Oracle Database. This is because Oracle Clusterware
hould always be at the same or later version as the database.
涉及到数据库而不是实例� ......
---sql的函数的使用(Oracle)
---dual的使用：哑元表：没有表需要查询的时候 可以用它
---select 'Hello World' from dual; ---结果：H ......
一、安装(略)
服务器端
1、windows:（略）
2、linux:待续...
客户端
待续...
--包括配置--
二、登陆
......
