熟悉并掌握創(chuàng)建表，插入記錄，查詢記錄，刪除記錄，修改記錄。

創(chuàng)建索引，刪除索引。

創(chuàng)建視圖，使用視圖，刪除視圖。

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實(shí)驗(yàn)內(nèi)容

現(xiàn)有一個(gè)單位內(nèi)部的小型圖書借閱系統(tǒng)，假設(shè)每本圖書的數(shù)量無限制，并且可以借給任何單位成員，每個(gè)單位成員可以借多本書，單位成員與圖書的關(guān)系是多對(duì)多的關(guān)系。假設(shè)系統(tǒng)中僅有三個(gè)關(guān)系模式。

數(shù)據(jù)表結(jié)構(gòu)

Reader表

Book表

RB表

部分提示（黃色底的代碼可以直接粘貼運(yùn)行）：

create user cc identified by ccpassword ;

grant resource, connect, DBA? to cc;

Declare

tmp integer default 0;

Begin

select count(*) into tmp from user_tables where table_name='RB';

if(tmp>0) then

execute immediate 'drop table RB';

end if;

select count(*) into tmp from user_tables where table_name='READER';

if(tmp>0) then

execute immediate 'drop table READER';

end if;

select count(*) into tmp from user_tables where table_name='BOOK';

if(tmp>0) then

execute immediate 'drop table BOOK';

end if;

end;

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問：為何要先刪去RB？能不能先刪去READER？

create table Reader

(

??? RNO????? varchar2(4) primary key,

??? Rname??? varchar2(10) not null,

??? Rsex?????? varchar2(2),

??? Rage?????? integer,

??? Rboss???? varchar2(10),

??? Raddress varchar2(30)

) ;

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R001','張三',20,'男','李四','416');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R002','張三',35,'女',null,'417');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R003','李四',30,'男',null,'416');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R004','王五',20,'男',null,'417');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R005','馬六',40,'男',null,'416');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R006','劉三',20,'男',null,'417');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R007','王四',40,'男','李四','416');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R008','李小龍',20,'男','李四','417');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R009','王小倩',40,'男','李四','416');

insert into Reader (RNO,Rname,Rage,Rsex,Rboss, Raddress) values('R010','王一小',20,'男','李四','417');

select Rname from Reader where Rboss='李四';

UPDATE reader SET Raddress='420' WHERE rboss='李四';

DELETE FROM reader WHERE rboss=NULL;

DROP TABLE reader;

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create table reader2 as select *? from reader; --創(chuàng)建表格reader2

查看這兩個(gè)數(shù)據(jù)表的結(jié)構(gòu)、內(nèi)容是否相同？分別執(zhí)行：

desc reader;

desc reader2;

也可以在可視化界面查看這兩個(gè)表所附帶的約束

update reader set RNO='R001' where Rname='張三';

表reader中的RNO是primary key,更新后的RNO與現(xiàn)存的RNO重復(fù)，違反唯一約束條件

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update reader2 set RNO='R001' where Rname='張三';

insert into reader2(RNO,Rname,Rsex,Rage,Rboss, Raddress) values(null,'lisi',null,null,null,null);

READER2

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DROP TABLE READER2;

create table Book

(

??? BNO????? varchar2(4),

??? Bname??? varchar2(50) not null,

??? Bauthor? varchar2(50),

??? Bpress??? varchar2(50),

??? Bprice??? numeric(6,2),

??? primary key(BNO)

);

insert into book (BNO,Bauthor,Bname, bpress, bprice) values('B001','嚴(yán)蔚敏','數(shù)據(jù)結(jié)構(gòu)','清華大學(xué)出版社',null);

insert into book (BNO,Bauthor,Bname, bpress, bprice) values('B002','唐發(fā)根','數(shù)據(jù)結(jié)構(gòu)','北航出版社',24);

insert into book (BNO,Bauthor,Bname, bpress, bprice) values('B003','王珊','數(shù)據(jù)庫(kù)原理','高等教育出版社',40);

insert into book (BNO,Bauthor,Bname, bpress, bprice) values('B004','張飛','數(shù)據(jù)庫(kù)原理','清華大學(xué)出版社',30);

insert into book (BNO,Bauthor,Bname, bpress, bprice) values('B005','王珊','數(shù)據(jù)庫(kù)原理','清華大學(xué)出版社',null);

create table RB

(

??? RNO varchar2(4),

??? BNO varchar2(4),

??? RBdate date default sysdate,

? ??primary key(RNO,BNO),

??? foreign key (RNO) references Reader(RNO),

??? foreign key (BNO) references Book(BNO)

);

insert into RB (RNO,BNO) values ('R001','B001');

insert into RB (RNO,BNO) values ('R001','B002');

insert into RB (RNO,BNO) values ('R001','B004');

insert into RB (RNO,BNO) values ('R002','B001');

insert into RB (RNO,BNO) values ('R003','B001');

insert into RB (RNO,BNO) values ('R004','B001');

insert into RB (RNO,BNO) values ('R004','B002');

insert into RB (RNO,BNO) values ('R005','B001');

insert into RB (RNO,BNO) values ('R006','B001');

insert into RB (RNO,BNO) values ('R006','B003');

insert into RB (RNO,BNO) values ('R006','B005');

insert into RB (RNO,BNO) values ('R006','B002');

insert into RB (RNO,BNO) values ('R006','B004');

初始數(shù)據(jù)

reader表

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book表中數(shù)據(jù)

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RB表中數(shù)據(jù)

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以下為查詢READER表中創(chuàng)建的約束類型，其中constraint_type為約束類型，該屬性值的取值Type Code如下表所示。（可以根據(jù)上課所講的實(shí)體完整性、參照完整性、用戶自定義完整性理解以下約束類型；直接在SQL DEVELOPER中雙擊表格也可以查看在表上所建立的約束）

select table_name,constraint_name,constraint_type from user_constraints where table_name ='READER';

?

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方法一：先把RB中所有’R010’的借書記錄都刪掉

方法二：修改數(shù)據(jù)表READER的結(jié)構(gòu)，允許級(jí)聯(lián)刪除（注：ORACLE不支持級(jí)聯(lián)更新）。

alter table rb add constraint MYFK foreign key(rno) references reader(rno) on delete cascade;

系統(tǒng)提示：SQL 錯(cuò)誤: ORA-02275: 此表中已經(jīng)存在這樣的引用約束條件

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可見，首先要先刪去原來的約束，因建表時(shí)沒給該約束命名，故應(yīng)查這個(gè)約束的名字，才能刪去。注意，這個(gè)名字由系統(tǒng)自動(dòng)賦值，不同的環(huán)境下約束名可能不同）：

alter table rb drop constraint SYS_C0011303;

alter table rb add constraint MYFK foreign key(rno) references reader(rno) on delete cascade;

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再執(zhí)行：delete from reader where rno='R010';

順利刪去一行，打開RB表，發(fā)現(xiàn)前面插入的('R010','B005')也不在了。

alter table reader ADD Rbirthday integer ;

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alter table reader DROP column Rbirthday;

alter table reader modify Raddress varchar2(50);

alter table book add constraint bp check (Bprice BETWEEN 10 and 100);

alter table Reader add constraint rr check (Rage BETWEEN 16 and 60);

drop table reader CASCADE;

drop table reader CASCADE CONSTRAINTS;

drop table rb CASCADE CONSTRAINTS;

drop table book CASCADE CONSTRAINTS;

索引的建立與刪除

create unique index myindex on reader(rname);

報(bào)告出錯(cuò)："cannot CREATE UNIQUE INDEX; duplicate keys found"

如何修改表格數(shù)據(jù)，再建索引

?解決方法很簡(jiǎn)單，要么把數(shù)據(jù)庫(kù)的數(shù)據(jù)清理掉；要么把你要?jiǎng)?chuàng)建唯一索引的那一列重復(fù)的數(shù)據(jù)刪掉。我選擇的是創(chuàng)建唯一索引的那一列重復(fù)的數(shù)據(jù)刪掉一個(gè)。

drop index myindex;

視圖

grant resource, connect, DBA? to cc;

否則系統(tǒng)顯示沒有創(chuàng)建視圖的權(quán)限。執(zhí)行完之后再回到CC的連接：

在ORACLE SQL Developer 的左上方：

CREATE VIEW V416 as select rno,rname,rage from reader where raddress='416'

確認(rèn)該視圖的存在：

select * from v416

SELECT rno,rname from v416 WHERE rage>30;

insert into v416( rno,rname,rage) values('R999','new reader',99);

select * from reader

select * from v416

插入成功了嗎？為什么通過視圖插入的紀(jì)錄在視圖中看不見？

剛插入數(shù)據(jù)條件不滿足此視圖的條件了

CREATE VIEW V417 as select rno,rname,rsex,rage,raddress from reader where raddress='417' with check option;

select * from v417

insert into v417( rno,rname,rage) values('R777','417 reader',66);

執(zhí)行不成功。

drop view v417;

CREATE VIEW V417 as select rno,rname,rsex,rage,raddress from reader where raddress='417' with check option;

insert into v417( rno,rname,rage,raddress) values('R777','417 reader',66,'417');

執(zhí)行成功。

select * from v416;

delete from v416 where rname='王小倩';

select * from v416;

CREATE VIEW FV417 as select * from V417 where RSEX='女';

select * from FV417;

SELECT * FROM V417;

Delete from v417 where v417.rno not in (SELECT rno from rb);

SELECT * FROM V417;

SELECT BNO,COUNT(*) FROM RB GROUP BY BNO;

?CREATE VIEW GV(BNO,COUNTS) ?AS? SELECT BNO,COUNT(*) FROM RB GROUP BY BNO;

?SELECT * FROM GV;

思考是否可以向GV中插入數(shù)據(jù)，為什么？

不可以向GV插入數(shù)據(jù)，因?yàn)镚V的內(nèi)容并非數(shù)據(jù)，而是數(shù)據(jù)和相關(guān)數(shù)據(jù)統(tǒng)計(jì)結(jié)果。

drop view v417

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觸發(fā)器（可不做，時(shí)間多再做）

參考PLSQL幫助文檔，試試建立一個(gè)觸發(fā)器。在用戶執(zhí)行刪除某個(gè)員工的時(shí)候觸發(fā)，該觸發(fā)器的功能是先刪除RB中該員工的借書記錄，然后刪除Reader中該員工記錄。

實(shí)驗(yàn)報(bào)告要求

寫出實(shí)驗(yàn)步驟及相關(guān)的SQL語(yǔ)句即可。

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