在實(shí)際的工作和學(xué)習(xí)中，為了分頁或查詢性能的需要，往往需要從數(shù)據(jù)庫查詢固定行數(shù)的記錄，不同的數(shù)據(jù)庫有不同的SQL語句來完成，在Oracle數(shù)據(jù)庫中，我們可以用下面的方法來實(shí)現(xiàn)，假設(shè)要從一個(gè)有百萬條記錄的表中每次取10萬條進(jìn)行處理，可以按下面步驟進(jìn)行：

1、創(chuàng)建表

Drop TABLE VEHICLE;

Create TABLE VEHICLE (

MAKE VARCHAR2(256) NOT NULL,

MODEL VARCHAR2(256),

REGISTRATION_NO NUMBER(15) NOT NULL primary key,

AGE NUMBER(2,1) NOT NULL,

CATEGORY VARCHAR(1) NOT NULL,

MILAGE NUMBER(15,2) NOT NULL,

LAST_SERVICE_DATE DATE NOT NULL

);

2、插入數(shù)據(jù)

可以用入下存儲(chǔ)過程進(jìn)行批量數(shù)據(jù)的插入，

create or replace PROCEDURE INSERT_APPOINTED_RECORDS

( startNum IN NUMBER, endNum IN NUMBER) AS

i number:=startNum;

j number:=endNum;

BEGIN

dbms_output.put_line(to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') );

While i<=j Loop

INSERT INTO

VEHICLE (REGISTRATION_NO,MAKE,MODEL,AGE,CATEGORY,MILAGE,LAST_SERVICE_DATE)

VALUES

(i,'test','test',3,'A',1000,SYSDATE);

i:=i+1;

End Loop;

dbms_output.put_line(to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') );

END INSERT_APPOINTED_RECORDS;

3、查詢固定行數(shù)的記錄

在Oracle數(shù)據(jù)庫中需要結(jié)合ROWNUM來完成，可以用如下方法來實(shí)現(xiàn)，如要取按ROWID排序的5000到10000之間的記錄

SELECT * FROM vehicle WHERE ROWNUM<10001 minus SELECT * FROM vehicle WHERE ROWNUM<5001;

如果需要按照某字段排序來查詢，如，按制造商Make來排序，就需要用到子查詢，性能就會(huì)有明顯的影響

SELECT * from (SELECT * FROM vehicle order by make) WHERE ROWNUM<10001 minus SELECT * from (SELECT * FROM vehicle order by make) WHERE ROWNUM<5001;

由于你對ROWNUM不能用像 Where rownum >10 and rownum <100這樣的語法，所以有點(diǎn)別扭，但是你可以通過以下方式來用：

select * from (select rownum r,REGISTRATION_NO,MAKE,MODEL,AGE,CATEGORY,MILAGE,LAST_SERVICE_DATE from vehicle) where r >=5000 and r<=10000;

或者

select * from (select rownum r,REGISTRATION_NO,MAKE,MODEL,AGE,CATEGORY,MILAGE,LAST_SERVICE_DATE from vehicle) where r between 5000 and 10000;

這樣就比較合符習(xí)慣了,不能用如下語句：

select * from (select * from vehicle order by make) where rownum between 5000 and 10000;

或者

select * from (select * from vehicle order by make) where rownum >= 5000 and rownum<=10000;