Tài liệu cực chất

7/23/2019 Ti liu cc cht

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Cc m hnh d liu

V Tuyt [email protected]

B mn Cc h thng thng tin, Vin CNTT&TTi hc Bch Khoa H Ni

2

M hnh d liu

M hnh d liu gm [Codd, 1980] Mt tp hp cc cu trc ca d liu Mt tp cc php ton thao tc vi cc d liu Mt tp cc rng buc v d liu

V d: m hnh mng, m hnh phn cp, m hnhquan h, m hnh thc th-lin kt, m hnhhng i tng

A data model is a plan for building a database*

*http://www.computerworld.com/databasetopics/data/story/0,10801,80205,00.html


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3

Vi nt v lch s

1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

M hnh

mng

M hnh

phn cp

M hnh

quan h

M hnh

hng itng

M hnh

quan h m rng

M hnh bn

cu trcDMS(65),

CODASYL

(71), IDMS,

IMS,

System

2k,

...

System R(81), DB2,

ORACLE, SQL

Server, Sybase, ...

O2,

ORION,

IRIS, ...

DB2,

ORACLE-

10i, SQL

Server ...

Lore

(97), ...

XML

dbXML,natix,

Tamino,...

M hnh

Thc th-lin ktIRDS(87),CDD+,...

4

Mt vi m hnh d liu

M hnh phn cp

M hnh mng

M hnh quan h

M hnh thc th - lin kt

M hnh hng itng

M hnh bn cu trc M hnh d liu ca XML


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5

t vn

c im ca cc m hnh d liu?

S khc nhau gia cc m hnh d liu?

Cc m hnh d liu ph bin ngy nay

6

M hnh d liu phn cp(Hierarchical data model)

S ra i Khong nm 60-65

Biu din: bng cy Quan h cha/con Mi nt c mt cha duy nht 1 CSDL = tp cc cy

Cc khi nim c bn Bn ghi Mc ni Cc php ton: GET, GET UNIQUE, GET NEXT, GET

NEXT WITHIN PARENT, ...


4/19

7

V d

lop

sinh_vien

giao_vien

diem_thi

mon_hoc mon_hoc

8

Nhn xt

u im D xy dng v thao tc Tng thch vi cc lnh vc t chc phn cp (vd:

t chc nhn s trong cc n v, ...) Ngn ng thao tc n gin (duyt cy)

Nhc im

S lp li ca cc kiu bn ghi d tha d liu vd liu khng nht qun Gii php: bn ghi o

Hn ch trong biu din ng ngha ca cc mc nigia cc bn ghi (ch cho php quan h 1-n)


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9

M hnh d liu mng(Network data model)

S ra i s dng ph bin t nhng nm 60, c nh ngha

li vo nm 1971

Biu din: bng th c hng Cc khi nim c bn

Tp bn ghi (record) Kiu bn ghi (record type) Cc trng (field)

Mc ni (link) Tn ca mc ni ch (owner) thnh vin (member): theo hng ca

mc ni Kiu mc ni: 1-1, 1-n, quy

Cc php ton Duyt: FIND, FIND member, FIND owner, FIND NEXT Th tc: GET

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V d

lop

sinh_vien

gom

giao_vien

diem_thico

mon_hoc

giang_day

co_diem

hoc


6/19

11

Nhn xt

u im n gin

C th biu din cc ng ngha a dng vi kiu bnghi v kiu mc ni

Truy vn thng qua php duyt th (navigation)

Nhc im S lng cc con tr ln

Hn ch trong biu din ng ngha ca cc mc nigia cc bn ghi

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M hnh d liu quan h(Relational data model)

S ra i vo nm 1970[Codd, 1970]

Biu din: di dng bng Cc khi nim c bn

Thuc tnh: mt tnh cht ring bit ca mt i tng Tn

Kiu, min gi tr Quan h: c nh ngha trn mt tp cc thuc tnh B gi tr: cc thng tin ca mt i tng thuc quan

h Kho:

Cc php ton: hp, giao, tch -cc, la chn,chiu, kt ni, ...


7/19

13

V d

maSV tenSV ngaysinh nam diachi lop

SV0011 Trn T. Bnh 1/4/1981 0 21 T. Q. B IT4

SV0025 Ng. . Trung 3/2/1980 1 56 . C. V IT5

SV0067 Trn M. Qu 26/3/1982 0 45 H. B. T IT6

SV0034 Ng. T. Phng 29/2/1980 0 86 L. T. N IT7

malop lop khoa GVCN loptruong

IT4 Tin 4 CNTT Ng. V. Anh Trn T. Bnh

IT5 Tin 5 CNTT L A. Vn Ng. . Trung

IT6 Tin 6 CNTT Ng. T. Tho Trn M. Qu

IT7 Tin 7 CNTT Ng. V. Qu Ng. T. Phng

maMH tenmon soHT

CNTT01 Nhp mn CSDL 4

CNTT02 Truyn DL v mng 4

CNTT03 Phn tch v thit kh thng 4

HTTT01 Qun l d n 3

MON_HOC

LOP

SINH_VIEN

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Nhn xt

u im Da trn l thuyt tp hp

Kh nng ti u ho cc x l phong ph

Nhc im Hn ch trong biu din ng ngha

Cu trc d liu khng linh hot


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M hnh d liu thc th - lin kt(Entity-Relational data model)

S ra i Xut pht t nhu cu m hnh ho ng ngha d liu v

pht trin phn mm xut 1975 [Chen, 1976] [Chen, 2002]

Biu din: bng s thc th - lin kt Cc khi nim c bn

Thc th: mt i tng trong th gii thc Thuc tnh: mt c tnh ca mt tp thc tho Kho:xc nh s duy nht ca 1 thc th

o Lin kt: mi lin h c ngha gia nhiu thc tho Mi lin kt c th c cc thuc tnho 1-1, 1-n, n-m, quy

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V d

sinh_vin lop

mon_hoc

gom

diem_thi chuong_trinh

maSV

tenSV

ngaysinh

nam

diachi

malop lop khoaGVCN

loptruong

maMH tenmon soHT


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17

Nhn xt

u im d dng biu din ci m con ngi nhn thc t th

gii thc

Biu din ng ngha phong ph ca cc thc th vquan h gia cc thc th

Nhc im Khng d dng nh x vo nhng cu trc lu tr

trn my tnh

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M hnh d liu hng i tng(Object-oriented data model)

S ra i Khong u nhng nm 90

Biu din: s lp

Cc khi nim c bn i tng: mt i tng trong th gii thc, c xc

nh bi mt nh danh duy nht

Thuc tnh: biu din mt c tnh ca i tng,

Phng thc : thao tc c thc hin trn i tng. Tt c cc truy nhp vo thuc tnh ca i tng u phi

c thc hin thng qua cc phng thc ny.

Lp: mt cch thc khai bo mt tp cc i tng cchung mt tp thuc tnh v phng thc


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V d

class sinh_vien {string maSV;string tenSV;date ngaysinh;boolean nam;string diachi;string lop;

stringten();stringngay_sinh();

stringdia_chi();

stringlop();voidgan_DC(stringDC_moi);

void gan_lop(stringlop);}

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V d

class lop {string tenlop;string khoa;

}

class sinh_vien {string maSV;string tenSV;date ngaysinh;

boolean nam;string diachi;lop lop_hoc;

}


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Nhn xt

u im Cho php nh ngha kiu i tng phc tp

Tnh cht: bao ng (encapsulation), k tha(heritage), a hnh (polymorphism)

Nhc im Cu trc lu tr phc tp v c th s dng nhiu

con tr

Kh nng ti u ho cc x l b hn ch trong nhiutrng hp

22

So snh v nh gi

khng h/q

khi s/d

nhiucontr

a dng

cu trcphc tp

a dng

khng cxem xt

(khng hiuqu)

kh lu tr

a dng

ti u hott

a dng

d dng vhiu qu

tng ia dng

t kh nngti u

n gin

d liu lp li

hn ch

t kh nngti u

n gin

s/d nhiu contr

hn ch

M hnh

HT

M hnh TT-

LK

M hnh

quan hM hnh

phn cpM hnh

mng

hiu qu catruy vn

kh nng truyvn

lu tr DL

biu din ngngha DL

Nhc li: M hnh d liu l mt tp hp cc khi nim dng m t cu trc ca mt CSDL


12/19

23

Phn loi cc m hnh

Phn cp

Mng

Quan h

Thc th-lin kt

ngngha

i tng - Quan h Hng i tng

Th h 1

Th h 2

Th h 3

Cc m hnh

da trnbn ghi

Cc m hnh

da trn

i tng

24

Bin i gia cc m hnh d liu

Yu cu Chuyn mt s d liu t mt m hnh d liu

sang mt m hnh khc

m bo tnh tng ng ca s d liungun v ch

Cc bin i tng ng gia cc m hnh Thc th/lin kt - mng Thc th/lin kt - hng i tng

Quan h - hng i tng


13/19

M hnh d liu quan h

26

c im

Da trn l thuyt tp hp

d dng nh x n cu trc lu tr vt l

Cc khi nim c bn Thut ng ton hc: quan h, b v thuc tnh

Thut ng hng d liu: bng, bn ghi v trng

c biu din bi lc quan h


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Thuc tnh - trng

/n: l mt tnh cht ring bit ca mt itng cn c lu tr trong CSDL phc vcho vic khai thc d liu v i tng K hiu: A

Tn thuc tnh: maSV, tenSV,ngaysinh,nam,diachi,lop

Kiu d liu, min gi tr (Dom(A)) text, number, boolean, date/time, memo maSV: text(10)

tenSV: text(30)

ngaysinh: datenam: boolean...

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Quan h - bng

/n: c xc nhtrn mt tp ccthuc tnh Ai

K hiu:

R(A1,A2, An)

R(A1,A2, An) Dom(A1)x x Dom(An)

Tn t: quy tc xc nh mi quan hgia cc thuc tnhAi

SINH_VIEN (maSV,tenSV,ngaysinh,nam, diachi,lop)

LOP(malop,ten,khoa)

lop SINH_VIEN[lop],malop LOP[malop]:lop = malop


15/19

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B - bn ghi

/n: cc thng tin ca mt i tng thucquan h

K hiu

t(a1,a2, an)

t(a1,a2, an) Dom(A1) x x Dom(An)

SV0011 Trn T. Bnh 1/4/1981 0 21 T. Q. B IT4

SV0025 Ng. . Trung 3/2/1980 1 56 . C. V IT5

SV0067 Trn M. Qu 26/3/1982 0 45 H. B. T IT6

SV0034 Ng. T. Phng 29/2/1980 0 86 L. T. N IT7

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Lc quan h

Lc quan h (S): l s tru tng ho caquan h mc cu trc ca mt bng 2chiu S = {Ri}

SINH_VIEN(maSV,tenSV, ngaysinh, nam, diachi,malop)

LOP(malop,lop, khoa, GVCN, loptruong)

MON_HOC(maMH,tenmon,soHT)

...

Th hin ca quan h: tp hp cc b gi trca quan h R vo mt thi im


16/19

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Kho

/n Cho R(A1,A2, An), K {Ai},

K l kho nu vi t1, t2 R, Ai K: t1.Kt2.K

SINH_VIEN (maSV,tenSV,ngaysinh,nam, diachi,lop)

T/c: K K {Ai} l kho K cng l kho

SINH_VIEN (maSV,tenSV,ngaysinh, nam, diachi,lop)

SINH_VIEN (maSV,tenSV,ngaysinh, nam, diachi,lop)

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Phn loi kho

Kho ti thiu Cho R(A1,A2, An),

K {Ai}, K l kho ti thiu nu

K l kho v !K Km K l kho

Kho ngoi

Cho R(A1,A2, An),R(A1,A2, Am), K {Ai},

K l kho ngoi ca Rtham chiu n quan hR nu K l kho chnhca R

SINH_VIEN (maSV,tenSV,ngaysinh,

nam, diachi,malop)

LOP(malop,lop, khoa, GVCN,loptruong)


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Mt s h qun tr CSDL quanh

MS. Access

MySQL

PostgreSQL

SQL Server

Oracle

DB2

33

nh ngha d liu

im chung Quan h

Kha chnh, kha ngoi, min gi tr

im ring C th h tr ha duy nht hay khng

C th cung cp giao din ha hay khng

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18/19

Kiu d liu

Cc kiu d liu c bn CHAR(n)

VARCHAR(n)

Int

Smallint

Numeric(p,d)

Real, double

float(n)

Datetime

Cc kiu d liu khc XML

Geometry

Variant 35

36


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Ti liu tham kho[Cattel,1997] R. G. G Cattel et al. The Object Database Standard: ODMG 2.0.

Morgan-Kaufmann, 1997

[Chen, 1976] The entity-relationship model: toward a unified view of data.

TODS, 1(1), 1976

[Chen, 2002] P. Chen. Entity-Relationship Modeling: Historical Events, Future

Trends, and Lessons Learned. Software Engeenering, 2002

[Codd, 1980] E. F. Codd. Data Models in Database Management. Proc. of

SIGMOD, 1980

[Codd, 1970] E. F. Codd. The relational model of data for large shared data

banks. CACM, 13(6), 1970

[McHugh,1997] J. McHugh et al. Lore: A Database Management System for

Semistructured Data. SIGMOD Record, 26(3), 1997

[XML] Extensible Markup Language. http://www.w3.org/XML

[Zdonik,1986] S. B. Zdonik et al. Language and Methodology for Object-

Oriented Database Environments. Proc. Of the Hawai

International Conference on System Sciences, 1986

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