Oracle中提供了對表進行分區的機制，通過表分區，可以將表空間中數據按照某種方式分別存放到特定的分區中。 表分區的作用：平衡 IO 操作，分區均勻，提高效率。

?? Oracle中表分區方法有：范圍分區法、散列分區法、復合分區法、列表分區法。

?范圍分區: 語法 Partition? by? range (); 適合數值型或日期型
? 示例：
?1?create?table ?Student
?2 (
?3?????Studentid?integer?not?null ,
?4?????Studentname?varchar2(20 ),
?5?????Score?integer
?6 )
?7?Partition?by ?range(Score)
?8 (
?9?????Partition?p1?values?less?than(60 ),
10?????Partition?p2?values?less?than(75 ),
11?????Partition?p3?values?less?than(85 ),
12?????Partition?p4?values ?less?than(maxvalue)
13 );

? 散列分區法： 根據Oracle內部散列算法存儲，語法 Partition by hash();
? 實例：
?1?create?table ?department
?2? (
?3?????Deptno?int ,
?4?????Deptname?varchar2(24 )
?5? )
?6?Partition?by ?hash(deptno)
?7? (
?8? ????Partition?p1,
?9? ????Partition?p2
10?);

? 復合分區法：由上面兩種方法復合而成
? 示例：
?1?create?table ?salgrade
?2? (
?3?????grade?number ,
?4?????losal?number ,
?5?????hisal?number
?6? )
?7?Partition?by ?range(grade)
?8?Subpartition?by ?hash(losal,hisal)
?9? (
10?????Partition?p1?values?less?than(10 ),
11? ??????(subpartition?sp1,subpartition?sp2),
12?????Partition?p2?values?less?than(20 ),
13? ??????(subpartition?sp3,subpartition?sp4)
14?)

? 列表分區法： 適合字符型 語法 Partition? by ?list()
? 實例：
?1?create?table ?customer
?2? (
?3?????custNo?int ,
?4?????custname?varchar(20 ),
?5?????custState?varchar(20 )
?6? )
?7?Partition?by ?list(custState)
?8? (
?9?????Partition?saia?values('中國','韓國','日本' ),
10?????Partition?Europe?values('英國','俄國','法國' ),
11?????Partition?ameria?values('美國','加拿大','墨西哥' ),
12? );
13?????

表分區維護：

添加分區:alter table student add partition p5 values less than(120);
刪除分區:alter table student drop partition p4;
截斷分區:alter table student truncate partition p5;
合并分區:alter table student merge partitions p3,p4 into partition p6;
? (轉載自http://www.blogjava.net/improviser/archive/2007/10/01/150073.html)?

轉載于:https://www.cnblogs.com/linsond/archive/2009/08/11/1543818.html

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