一、概述
对于某些需要通过数据库与大量数据打交道的软件来说，处理性能相当的重要。为了保证软件能够将所有数据处理完而不至于崩溃，分批处理的思想应运而生。分批处理的具体做法是编写SQL语句，每次返回规定条数的数据给软件处理，待这一批数据处理完之后，再接着处理下一批。
本文通过对具体的数据库表(tb_employeeinfo)的操作过程，展示了ORACLE和SYBASE数据库中分批处理SQL语句的编写方法。

二、ORACLE数据库中的处理
首先，建立tb_employeeinfo表，其定义如下：

begin
execute immediate 'drop table tb_employeeinfo CASCADE CONSTRAINTS';
EXCEPTION WHEN OTHERS THEN NULL;
end;

/
create table tb_employeeinfo
(
    employeeno    varchar2(20)     not null,    -- no. of employee
    employeename  varchar2(20)     not null,    -- name of employee
    employeeage   int              not null     -- age of employee
);
create unique index idx1_tb_employeeinfo on tb_employeeinfo(employeeno);
prompt 'create table tb_employeeinfo ok';
commit;

接着，在tb_employeeinfo表中插入7条数据，如下：

insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1000', 'ZhangSan', 20); insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1001', 'LiSi', 21); insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1002', 'WangWu', 21); insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1003', 'ZhouLiu', 22); insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1004', 'SunQi', 22); insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1005', 'LiuBa', 23); insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1006', 'ChenShi', 25); 

如果我们想要一次性从tb_employeeinfo表中查询出5条数据，该如何处理呢？
ORACLE数据库中有一个rownum用在查询(select)语句中来限制每次执行之后返回的数据条数。例如，本次要从tb_employeeinfo表中返回5条数据，则编写SQL语句如下：

select employeeno, employeename, employeeage from tb_employeeinfo where rownum<=5;

执行结果如下：

SQL> select employeeno, employeename, employeeage from tb_employeeinfo where rownum<=5; EMPLOYEENO EMPLOYEENAME EMPLOYEEAGE A1000 ZhangSan 20 A1001 LiSi 21 A1002 WangWu 21 A1003 ZhouLiu 22 A1004 SunQi 22 

三、SYBASE数据库中的处理
首先，建立tb_employeeinfo表，其定义如下：

if exists(select * from sysobjects where name='tb_employeeinfo') drop table tb_employeeinfo go create table tb_employeeinfo ( employeeno varchar(20) not null, -- no. of employee employeename varchar(20) not null, -- name of employee employeeage int not null -- age of employee ) go create unique index idx1_tb_employeeinfo on tb_employeeinfo(employeeno) go print 'create table tb_employeeinfo ok' go 

接着，在tb_employeeinfo表中插入7条数据，如下：

insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1000', 'ZhangSan', 20) insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1001', 'LiSi', 21) insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1002', 'WangWu', 21) insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1003', 'ZhouLiu', 22) insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1004', 'SunQi', 22) insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1005', 'LiuBa', 23) insert into tb_employeeinfo(employeeno, employeename, employeeage) values('A1006', 'ChenShi', 25) 

如果我们想要一次性从tb_employeeinfo表中查询出5条数据，该如何处理呢？
在SYBASE数据库中，可以利用“set rowcount X”语句来实现查询条数的限制。例如，本次要从tb_employeeinfo表中返回5条数据，则编写SQL语句如下：

set rowcount 5 select employeeno, employeename, employeeage from tb_employeeinfo set rowcount 0 

执行结果如下：

employeeno employeename employeeage A1000 ZhangSan 20 A1001 LiSi 21 A1002 WangWu 21 A1003 ZhouLiu 22 A1004 SunQi 22