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¶ÔÓÚrownumÀ´ËµËüÊÇoracleϵͳ˳Ðò·ÖÅäΪ´Ó²éѯ·µ»ØµÄÐеıàºÅ£¬·µ»ØµÄµÚÒ»ÐзÖÅäµÄÊÇ1£¬µÚ¶þÐÐÊÇ2£¬ÒÀ´ËÀàÍÆ£¬Õâ¸öα×ֶοÉÒÔÓÃÓÚÏÞÖÆ²éѯ·µ»ØµÄ×ÜÐÐÊý£¬¶øÇÒrownum²»ÄÜÒÔÈκαíµÄÃû³Æ×÷Ϊǰ׺¡£
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ÀýÈç±í£ºstudent(ѧÉú)±í£¬±í½á¹¹Îª£º
ID¡¡¡¡¡¡    char(6)¡¡¡¡¡¡¡¡¡¡ --ѧºÅ
name¡¡¡¡¡¡¡¡VARCHAR2(10)¡¡¡¡¡¡--ÐÕÃû
create table student (ID char(6), name VARCHAR2(100));
insert into sale values('200001',‘ÕÅÒ»’);
insert into sale values('200002',‘Íõ¶þ’);
insert into sale values('200003',‘ÀîÈý’);
insert into sale values('200004',‘ÕÔËÄ’);
commit;
(1) rownum ¶ÔÓÚµÈÓÚijֵµÄ²éѯÌõ¼þ
Èç¹ûÏ£ÍûÕÒµ½Ñ§Éú±íÖеÚÒ»ÌõѧÉúµÄÐÅÏ¢£¬¿ÉÒÔʹÓÃrownum=1×÷ΪÌõ¼þ¡£µ«ÊÇÏëÕÒµ½Ñ§Éú±íÖеڶþÌõѧÉúµÄÐÅÏ¢£¬Ê¹ÓÃrownum=2½á¹û²é²»µ½Êý¾Ý¡£ÒòΪrownum¶¼ÊÇ´Ó1¿ªÊ¼£¬µ«ÊÇ1ÒÔÉϵÄ×ÔÈ»ÊýÔÚrownum×öµÈÓÚÅжÏÊÇʱÈÏΪ¶¼ÊÇfalseÌõ¼þ£¬ËùÒÔÎÞ·¨²éµ½rownum = n£¨n>1µÄ×ÔÈ»Êý£©¡£
SQL> select rownum,id,name from student where rownum=1;£¨¿ÉÒÔÓÃÔÚÏÞÖÆ·µ»Ø¼Ç¼ÌõÊýµÄµØ·½£¬±£Ö¤²»³ö´í£¬È磺ÒþʽÓα꣩
SQL> select rownum,id,name from student where rownum=1;
    ROWNUM ID     NAME
---------- ------ ---------------------------------------------------
         1 200001 ÕÅÒ»
SQL> select rownum,id,name from student where rownum =2;
    ROWNUM ID     NAME
---------- ------ ---------------------------------------------------
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   Èç¹ûÏëÕÒµ½´ÓµÚ¶þÐмǼÒÔºóµÄ¼Ç¼£¬µ±Ê¹ÓÃrownum>2ÊDz鲻³ö¼Ç¼µÄ£¬Ô­ÒòÊÇÓÉÓÚrownumÊÇÒ»¸ö×ÜÊÇ´Ó1¿ªÊ¼µÄαÁУ¬Oracle ÈÏΪrownum> n(n>1µÄ×ÔÈ»Êý)ÕâÖÖÌõ¼þÒÀ¾É²»³ÉÁ¢£¬ËùÒԲ鲻µ½¼Ç¼
SQL> select rownum,id,name from student where rownum >2;
ROWNUM ID     NAME
---------- ------ ---------------------------------------------------
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Oracleѧϰ±Ê¼Çժ¼4

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CREATE Student(
[Studentid][Int]IDENTITY(1,1)NOT NULL primary key,--Ö÷¼ü
[StudentName][char]NOT NULL
)
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CREATE Subject(
[SubjectID][char]NOT NULL primary key,          --Ö÷¼ü
[SubjectName][char]NOT NULL
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Oracleѧϰ±Ê¼Çժ¼5

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  --IDENTITYÊôÐÔ
  create table test(
    xh int identity(1,2) primary key,
    name varchar(20)
);
  insert into test(name) values ('mike');
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Oracleѧϰ±Ê¼Çժ¼8

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