05 Database Models

Ins to FOR-IAN V. SANDOVAL
truc r:
fvs nd va ya o o
a o l@ ho .c m
http w .s e ha .ne a o l
://w w lid s re t/fvs nd va

 A d ta a em d l is a the ry o s e ific tio d s rib
a bs oe o r p c a n e c ing
ho ad ta a eiss ture a us d
w a bs truc d nd e .
 Als kno n a Database Schema
o w s
 Sc m s a g ne lly s re in a d ta d tio ry a
he a re e ra to d a ic na nd
o n us d to re r to a g p a d p tio o the
fte e fe ra hic l e ic n f
d ta a es ture
a b s truc .
 It a o d fine a s t o o e tio tha c n b p rfo e
ls e s e f p ra ns t a e e rm d
o thed ta
n a .

1. Hie rc a Mo e
ra hic l dl
2 Ne o Mo e
. tw rk dl
3 Re tio l Mo e
. la na dl
4 Entity-Re tio hipMo e
. la ns dl
5 Ob c la na Mo e
. je t-Re tio l dl
6 Ob c Mo e
. je t dl

1. Fla Mo e
t dl
2 As o ia Mo e
. s c tive d l
3 C nc p
. o e t-Orie dMo e
nte dl
4 Entity-Attrib -Va Mo e
. ute lue d l
5 Info a n Mo e
. rm tio dl
6 Multi-Dim ns na Mo e
. e io l dl
7. Se a Da Mo e
m ntic ta d l
8 Se i-Struc
. m tureMo e
dl
9 Sta Sc m Mo e
. r he a d l
10 XML Da b s Mo e
. ta a e d l
11. C nte Mo e
o xt dl

 A hie rc a d ta m d l is a d ta m d l in w h the
ra hic l a oe a oe hic
d taiso a dinto atre -likes ture
a rg nize e truc .
 All a ute o a s e ific re o a lis d und r a
ttrib s f pc c rd re te e n
entity typ .
e
 An e ntity typ isthee uiva nt o ata le
e q le f b .
 Ea h ind ua re o is re re e d a a ro a a
c ivid l c rd p s nte s w nd n
a utea ac lum
ttrib s o n.
 Entity typ s a re te to e c o r us
e re la d a h the ing 1: N
m p ing a okno n a o -to a re tio hip .
a p , ls w s ne -m ny la ns s
 IMS is the m s re o nize a us d hie rc a
o t c g d nd e ra hic l
d ta a ed ve p db IBM.
a b s e lo e y

An o a tio ha re o s o e p ye s in a ta le
rg niza n d c rd f m lo e b
(entity typ ) c lle "Em lo e ". In the ta le the w uld
e a d p ye s b re o
b a ute /c lum s h a Firs Na e La t Na e J b
e ttrib s o ns uc s t m, s m, o
Na e a W g . The c m a a o ha d ta a o the
m nd a e o p ny ls s a b ut
e p ye ’ c re in a s p ra ta le c lle "C re
m lo e s hild n e a te b a d hild n"
w a ute s h a Firs Na e La t Na e a d teo
ith ttrib s uc s t m , s m , nd a f
birth. TheEm lo eta lere re e ap re s g e a
p ye b p s nts a nt e m nt nd
the C re ta le re re e a C
hild n b p s nts hild s g e The e tw
e m nt. s o
s g e fo a hie rc w re a e p ye m y ha
e m nts rm ra hy he n m lo e a ve
m ny c re b e c c
a hild n, ut a h hildm y o ha o p re
a nly ve ne a nt.

EmpNo Designation ReportsTo
10 Director
20 Senior Manager 10
30 Typist 20
40 Programmer 20

•W n theP a Ke a ac m o fie , it isc lle a
he rim ry y s o m n ld a d
foreign key in thes c nd ta le
eo b .

 A tre s tureis a w y o re re e
e truc a f p s nting thehie rc a
ra hic l
natureo as turein ag p a fo .
f truc ra hic l rm
 It is na e a "tre s ture b c us the c s ic
md e truc " e a e la s
re re e tio lo ks a b like a tre , e n tho h the
p s nta n o it e ve ug
tre is g ne lly s w up id d w c m a d w a
e e ra ho n s e o n o p re ith
re l tre ; tha is to s y w the ro t a the to a the
a e t a ith o t p nd
le ve a theb tto .
a s t o m

A tre s ture s w
e truc ho ing the p s ib hie rc a
o s le ra hic l
o a tio o a e yc p d .
rg niza n f n nc lo e ia

1. Inte t: Us ne hie rc Do um nt Ob c Mo e
rne e t ra hy, c e je t d l's
lo ic l s ture Ya o s je t ind x, Op n
g a truc , ho ! ub c e e
Dire to P je t
c ry ro c
2. Info a n m na e e De e De im l Sys m
rm tio a g m nt: w y c a te
3. Ma g m nt: hie rc a o a tio l s ture
na e e ra hic l rg niza na truc s
4. C m ute Sc nc : b ry s a h tre Re -Bla k Tre
o p r ie e ina e rc e d c e
AVL tre e
5. Bio g e lutio ry tre
lo y: vo na e
6. Bus s : p m s llings he e
ine s yra id e c m
7. P je t m na e e w rk b a o n s ture
ro c a g m nt: o re kd w truc
8. Ling tic (s x): P s s turetre s
uis s ynta hra e truc e

The a m ny w ys o vis lly re re e
re re a a f ua p s nting tree
s ture . Alm s a a , the e b il d w to va tio , o
truc s o t lw ys s o o n ria ns r
c m ina ns o afe b s s s
o b tio , f w a ic tyle :
1. C s ic l no e
la s a d -link d g m
ia ra s
2 Ne te s ts
. s d e
3 La re "ic le d g m
. ye d ic " ia ra s
4 Outline a tre vie s
. s nd e w
5 Ne te p re s s
. s d a nthe e

C s ic l no e
la s a d -link d g m , tha c nne t no e
ia ra s t o c ds
to e r w lines g e :
g the ith e m nts

encyclopedia
/
science culture
/
art craft

La re "ic le d g m tha us a nm nt/a ja e y:
ye d ic " ia ra s t e lig e d c nc

+-------------------+
| encyclopedia |
+---------+---------+
| science | culture |
+---------+---+-----+
|art|craft|
+---+-----+

Lis o d g m tha us ind nta n, s m tim s c lle
ts r ia ra s t e e tio o e e a d
"outline " o "tre vie s
s r e w ":

encyclopedia
science
culture
art
craft

Ne te p re s s ac rre p nd nc firs no e b Sir
s d a nthe e , o s o e e t tic d y
Arthur C yle
a y

science, ((art, craft)culture)encyclopedia

 A hie rc a q ry isatyp o SQL q ry tha ha le
ra hic l ue e f ue t nd s
hie rc a m d l d ta
ra hic l o e a .
 Sta a SQL s e ifie hie rc a q rie b w y o
nd rd p c s ra hic l ue s y a f
re urs common table expressions (C ). Re urs
c ive TEs c ive
CTEs a s p rte b s te s inc ing IBM DB2
re up o d y ys m lud ,
Mic s ft SQL Se r, Fire ird 2 nd P s re
ro o rve b .1a o tg SQL 8 .
.4
 An a rna
lte tive s x is the no ta a C
ynta n-s nd rd ONNECT
BY c ns t. "CONNECT BY is s p rte b
o truc " up o d y
Ente ris DB a Ora led ta a e
rp e nd c a bs.

SELECT select_list
FROM table_expression
[ WHERE ... ]
[ START WITH start_expression ]
CONNECT BY { PRIOR parent_expr = child_expr | child_expr = PRIOR parent_expr }
[ ORDER SIBLINGS BY column1 [ ASC | DESC ] [, column2 [ ASC | DESC ] ] ...
[ GROUP BY ... ]
[ HAVING ... ]
...

SELECT LEVEL, LPAD (' ', 2 * (LEVEL - 1)) || ename "employee", empno, mgr
FROM emp START WITH mgr IS NULL
CONNECT BY PRIOR empno = mgr;

 Theo ut o theq ry w uldlo k like
utp f ue o o :
level | employee | empno | mgr
-------+-------------+-------+------
1 | KING | 7839 |
2 | JONES | 7566 | 7839
3 | SCOTT | 7788 | 7566
4 | ADAMS | 7876 | 7788
3 | FORD | 7902 | 7566
4 | SMITH | 7369 | 7902
2 | BLAKE | 7698 | 7839
3 | ALLEN | 7499 | 7698
3 | WARD | 7521 | 7698
3 | MARTIN | 7654 | 7698
3 | TURNER | 7844 | 7698
3 | JAMES | 7900 | 7698
2 | CLARK | 7782 | 7839
3 | MILLER | 7934 | 7782
(14 rows)

 The network model is a d ta a e m d l c nc ive a a
a bs oe o e d s
fle le w y o re re e
xib a f p s nting o je ts a
b c nd their
re tio hip .
la ns s
 The ne otw rk m d l o a s d ta us
oe rg nize a ing two
fund m nta c ns ts c lle re o sa s ts
a e l o truc , a d c rd nd e .
 Re o s c nta fie s (w h m y b o a d
c rd o in ld hic a e rg nize
hie rc a
ra hic lly, a in the p g m ing la ua e
s ro ra m ng g
 C ts (no to b c nfus d w m the a a s ts d fine
SeOBOL) t e o e ith a m tic l e ) e
o -to a re tio hip b tw e re o s o o ne
ne -m ny la ns s e e n c rd : ne w r,
m ny m m e .
a e b rs

 The ne o m d l is a va tio o the hie rc a
tw rk o e ria n n ra hic l
m d l.
oe
 Theo e tio o thene o m d l a na a na in
p ra ns f tw rk o e re vig tio l
s : a p g m m inta
tyle ro ra a ins a c nt p s n, a
urre o itio nd
na a s fro o re o to a the b fo w the
vig te m ne c rd no r y llo ing
re tio hip in w h there o p rtic a s
la ns s hic c rd a ip te .
 Re o sc n a ob lo a d b s p
c rd a ls e c te y up lyingke va s
y lue .

1. Turb IMAGE
o
IMAGE is the p a re s n tha the HP 0 0 w s a
rim ry a o t 30 a
s c s . It is a re b , s p , fa t d ta a efo MP
uc e s lia le im le s a b s r E.
Afte a o a d c d o e nc m nts it w s re m d
r b ut e a e f nha e e a na e
Turb IMAGE, the Turb IMAGE/XL a r the P
o n o fte A-
RISC m ra n. P g m c n a c s a up a
ig tio ro ra s a c e s nd d te
re o s us IMAGE intrins s To a it is kno n a
c rd ing ic . d y w s
IMAGE/SQL b c us it inc e a SQL (Struc d
ea e lud s n ture
Que La ua e fro nd a c nt-s rve s p rt
ry ng g ) nte nd lie e r up o
fo P a c s o .
r C c e s rs

2 IDMS(Inte ra d Da b s Ma g m nt Sys m
. g te ta a e na e e te )
IDMS (Inte ra d Da b s Ma g m nt Sys m is a
g te ta a e na e e te )
(ne o C
tw rk) ODASYL d ta a e m na e e s te
a bs a g m nt ys m
firs d ve p d a B.F. Go d h a la r m rke d b
t e lo e t o ric nd te a te y
C ullina Da b s Sys m (re m d C
ne ta a e te s na e ulline in
t
19 3 Sinc 19 9 the p d t ha b e o ne b
8 ). e 8 ro uc s en w d y
C m ute As o ia s w re m dit C
o p r s c te , ho na e A-IDMS.

3 RDM Em e d d
. bde
RDM Embedded (fo Raima Database Manager) is
r
a hig p rfo ing AC
h e rm ID-c m lia
o p nt e b d e
medd
d ta a e m na e e lib ry d s ne fo b th d k
a b s a g m nt ra e ig d r o is
bsd a
ae nd in-m m ry e b d e s te s a
e o m e d d ys m nd
a p a ns RDM Em e d d c n run p ly in m in
p lic tio . bde a ure a
m m ry (a o kno n a a in-m m ry d ta a e o
e o ls w s n e o a bs, r
IMDB), p ly o d k, o in m d m d s ring p rts
ure n is r ixe o e to a
o the d ta e in-m m ry a p rts o is RDM
f a st e o nd a n-d k.
Em e d d ha a p ve tra k re o firs re a e in
bde s ro n c c rd t le s d
19 4 c unting o r 2 ,0 0 0 ins lla ns in a
8 o ve 5 0 ,0 0 ta tio ll
kind o e b d e s te sa a p a ns
s f m e d d ys m nd p lic tio .

4 RDM Se r
. rve
RDM Se r isAC
rve ID-c m lia c nt/s rve
o p nt lie e r
e b d e d ta a es te d s ne fo b th d k
m e d d a b s ys m e ig d r o is
b s da in-m m ry e b d e s te sa
a e nd e o m e d d ys m nd
a p a ns
p lic tio .

 A d ta a e b s d o the re tio l m d l d ve p d b
a b s ae n la na o e e lo e y
E.F. C d .
od
 Re tio l d ta a e a w the d finitio o d ta
la na a b s llo s e n f a
s ture , s ra e a re va o e tio a inte rity
truc s to g nd trie l p ra ns nd g
c ns ints
o tra .
 A d ta a e the d ta a re tio b tw e the a
a bs a nd la ns e e n m re
o a d in ta le .
rg nize b s
 A ta le is a c lle tio o re o s a e c re o in a
b o c n f c rd nd a h c rd
ta lec nta thes m fie s
b o ins a e ld .

1. Va sa a m
lue re to ic
2 Ea h ro isuniq
. c w ue
3 C lum va so thes m kind
. o n lue f a e
4 Thes q nc o c lum isins nific nt
. e ue e f o n ig a
5 Thes q nc o ro isins nific nt
. e ue e f w ig a
6 Ea h c lum ha auniq na e
. c o n s ue m

 This p p rty im lie tha c lum in a re tio l ta le
ro e p s t o ns la na b
a no re e tingg upo a ys
re t p a ro r rra .
 Suc ta le a re rre to a b ing in the "firs no a
h b s re fe d s e t rm l
fo " (1NF).
rm
 The a m va
to ic lue p p rty o re tio l ta le is
ro e f la na b s
im o nt b c us it is o o the c rne to s o the
p rta e a e ne f o rs ne f
re tio l m d l.
la na o e
 The ke b ne o the o va
y e fit f ne lue p p rty is tha it
ro e t
s p sd tam nip tio lo ic
im lifie a a ula n g .

 This p p rty e ure tha no tw ro s in a re tio l
ro e ns s t o w la na
ta lea id ntic l.
b re e a
 The is a le s o c lum o s t o c lum , the
re t a t ne o n, r e f o ns
va so w h uniq ly id ntify e c ro in theta le
lue f hic ue e ah w b .
 Suc c lum a c lle p a ke .
h o ns re a d rim ry ys
 This p p rty g ra e tha e ry ro in a re tio l
ro e ua nte s t ve w la na
ta le is m a
b e ning a tha a s e ific ro c n b
ful nd t pc w a e
id ntifie b s e ifyingthep a ke va .
e d y pc rim ry y lue

 In re tio l te sthism a tha a va sin ac lum
la na rm e ns t ll lue o n
c m fro thes m d m in.
o e m a e o a
 A d m in isas t o va sw h ac lum m y ha .
o a e f lue hic o n a ve
 This p p rty s p s d ta a c s b c us d ve p rs
ro e im lifie a c e s e a e e lo e
a us rs c n b c rta o thetyp o d ta c nta d in
nd e a e e in f e f a o ine
ag n c lum
ive o n.
 It a o s p sd tava a n.
ls im lifie a lid tio
 Be a e a va s a fro the s m d m in, the
c us ll lue re m a e o a
d m in c n b d fine a e rc d w the Da
o a a e e d nd nfo e ith ta
Definitio La ua e(DDL) o thed ta a es ftw re
n ng g f a bs o a .

 This p p rty s te tha the o e
ro e ta s t rd ring o the c lum in
f o ns
there tio l ta leha no m a
la na b s e ning .
 C lum c n b re ve in a o e a in va us
o ns a e trie d ny rd r nd rio
s q nc s
e ue e .
 It e b s m ny us rs to s re the s m ta le w ut
na le a e ha a e b itho
c nc rn o ho theta leiso a d
o e f w b rg nize .
 It a o p rm the p ic l s ture o the d ta a e to
ls e its hys a truc f a bs
c ng w ut a c
ha e itho ffe tingthere tio l ta le .
la na b s

 This p p rty is a lo o the o a o b a p s to
ro e na g us ne b ve ut p lie
ro sins a o c lum .
w te d f o ns
 Ad inginfo a n to are tio l ta leiss p d a
d rm tio la na b im lifie nd
d e no a c e tingq rie .
o s t ffe t xis ue s
 Ad inginfo a n to are tio l ta leiss p d a
d rm tio la na b im lifie nd
d e no a c e tingq rie .
o s t ffe t xis ue s

 Be a e the s q nc o c lum is ins nific nt,
c us e ue e f o ns ig a
c lum m t b re re e b na e a no b
o ns us e fe nc d y m nd t y
 p so n. n na e ne d no b uniq w
o itio
A c lum m e t e ue ithin a e
n ntire
d ta a eb o w
a b s ut nly ithin theta letow h it b lo s
b hic e ng .

 An o je t-re tio l
b c la na d ta a e (ORD), o o je t-
a bs r b c
re tio l d ta a e m na e e s te (ORDBMS), is
la na a b s a g m nt ys m
a d ta a e m na e e s te (DBMS) s ila to a
a b s a g m nt ys m im r
re tio l d ta a e
la na a b s
 An o je t-o nte d ta a e m d l: o je ts c s e a
b c rie d a b s o e b c , la s s nd
inhe nc a d c s p rte in d ta a e s he a
rita e re ire tly up o d a b s c ms
a in theq ry la ua e
nd ue ng g .
 It s p rts e ns n o the d ta m d l w c to
up o xte io f a o e ith us m
d ta e a m tho s
a -typ s nd e d .

 An o je t-re tio l d ta a e c n b s id to p vid a
b c la na a b s a e a ro e
m d g und b tw e re tio l d ta a e a o je t-
id le ro e e n la na a b s s nd b c
o nte d ta a e (OODBMS).
rie d a b s s
 In o je t-re tio l d ta a e , thea p a h ise s ntia
b c la na a b s s p ro c s e lly
tha o re tio l d ta a e : the d ta re id s in the
t f la na a b s s a s e
d ta a e a is m nip te c lle tive w q rie in
a b s nd a ula d o c ly ith ue s
aq ry la ua e
ue ng g ;
 a the o r e m a OODBMSe in w h the
t the xtre e re s hic
d ta a e is e s ntia a p rs te o je t s re fo
a bs s e lly e is nt b c to r
s ftw re w n in a o je t-o nte p g m ing
o a ritte n b c rie d ro ra m
la ua e w a p g m ing AP fo s ring a
ng g , ith ro ra m I r to nd
re ving o je ts a little o no s e ific s p rt fo
trie b c , nd r pc up o r
q rying
ue .

Example of Object-Relational Model

In c m uting o je t m d l ha tw re te b d tinc
o p , b c o e s o la d ut is t
ma e ning :
s
1. The p p rtie o o je ts in g ne l, in a s e ific
ro e s f b c e ra pc
c m ute p g m ing la ua e te hno g no tio
o p r ro ra m ng g , c lo y, ta n
o m tho o g tha us s the . Fo e m le the J va
r e d lo y t e m r xa p , a
o je t m d l, the C
b c oe OM o je t m d l, o the o je t
b c oe r b c
m d l o OMT. Suc o je t m d ls a us lly d fine
oe f h b c o e re ua e d
us ing c nc p s h a c s , m s a e inhe nc ,
o e ts uc s la s e s g , rita e
p lym rp m a e a s tio The is a e ns
o o his , nd nc p ula n. re n xte ive
lite tureo fo a d o je t m d ls a a s s t o the
ra n rm lize b c o e s ub e f
fo a s m ntic o p g m ingla ua e .
rm l e a s f ro ra m ng g s

2 A c lle tio o o je ts o c s e thro h w h a
. o c n f b c r la s s ug hic
p g m cn e m
ro ra a xa ine a m nip te s m s e ific
nd a ula o e p c
p rts o its w rld In o r w rd , the o je t-o nte
a f o . the o s b c rie d
inte c to s m s rvic o s te . Suc a inte c is
rfa e o e e e r ys m h n rfa e
s id to b theo je t m d l o there re e d s rvic o
a e b c oe f p s nte e e r
s te . Fo e m le the Do um nt Ob c Mo e
ys m r xa p , c e je t dl
(DOM) isac lle tio o o je tstha re re e ap g in
o c n f b c t p s nt a e
a w b b w e us d b s rip p g m to e m a
e ro s r, e y c t ro ra s xa ine nd
d m a c ng thep g . The isaMic s ft Exc l
yna ic lly ha e ae re ro o e
o je t m d l fo c ntro
b c oe r o lling Mic s ft Exc l fro
ro o e m
a the p g m a the ASC
no r ro ra , nd OM Te s o e Drive is
le c p r
a o je t m d l fo c ntro
n b c oe r o lling a a tro m a
n s no ic l
te s o e
le c p .

Example of Object Model for Paint Application

 The Entity-Re tio hip (ER) m d l w s o ina
la ns o e a rig lly
p p s d b P te in 19 [C n76 a a w y to unify
ro o e y e r 76 he ] s a
thene o a re tio l d ta a evie s
tw rk nd la na a b s w
 ER m d l isa c nc p l d ta m d l tha vie sthere l
oe o e tua a oe t w a
w rld a e
o s ntitie a re tio hip .
s nd la ns s
 A b s c m o nt o the m d l is the Entity-
a ic o p ne f oe
Re tio hip d g mw h isus d to vis lly re re e
la ns ia ra hic e ua p s nt
d tao je ts
a b c .

 It m p w ll to there tio l m d l. Thec ns tsus d
as e la na o e o truc e
in the ER m d l c n e s
o e a a ily b tra fo e into
e ns rm d
re tio l ta le .
la na b s
 It is s p a e s to und rs nd w a m
im le nd a y e ta ith inim o
um f
training The fo , the m d l c n b us d b the
. re re oe a e e y
d ta a e d s ne to c m unic te the d s n to the e
a b s e ig r o m a e ig nd
us r.
e
 In a d n, the m d l c n b us d a a d s n p n b
d itio o e a e e s e ig la y
the d ta a e d ve p r to im le e a d ta m d l in
a b s e lo e p m nt a oe
s e ificd ta a em na e e s ftw re
pc a b s a g m nt o a .

The ER m d l vie s the re l w rld a a c ns t o
oe w a o s o truc f
entitie a a s c tio b tw e e
s nd s o ia n e e n ntitie .
s
1. Entities
2 Special Entity Types
.
3 Attributes
.
4 Relationships
.
5 Classifying Relationships
.
6 Degree of a Relationship
.
7. Connectivity and Cardinality
8 Direction
.

9 Type
.
10 Existence
.
11. Generalization Hierarchies
12 ER Notation
.

 Entitie a the p ip l d ta o je t a o w h
s re rinc a a b c b ut hic
info a n isto b c lle te .
rm tio e o c d
 Entitie a us lly re o niza le c nc p , e r
s re ua cg b o e ts ithe
c nc te o a s c s h a p rs n, p c s thing , o
o re r b tra t, uc s e o la e , s r
e ntsw h ha re va eto thed ta a e
ve hic ve le nc a bs.
 Entitie a c s ifie a ind p nd nt o d p nd nt (in
s re la s d s e e e r e e e
s m m tho o g s the te s us d a s ng a
o e e d lo ie , rm e re tro nd
w a re p c ly).
e k, s e tive
 An ind p nd nt e
ee e ntity is o tha d e no re o
ne t o s t ly n
a the fo id ntific tio
no r r e a n.
 A d p nd nt e
e e e ntity is o tha re s o a the fo
ne t lie n no r r
id ntific tio
e a n.

 An entity o c nc (a o c lle a ins nc ) is a
c urre e ls a d n ta e n
ind ua o c nc o a e
ivid l c urre e f n ntity.
 An o c nc is a lo o to a ro in the re tio l
c urre e na g us w la na
ta le
b .

 As o ia
s c tive entitie (a o kno n a inte e tio e
s ls w s rs c n ntitie )
s
a e
re ntitie us d to a s c te tw o m re e
s e s o ia o r o ntitie ins
o e to re o ileam ny-to a re tio hip
rd r c nc a -m ny la ns .
 Sub e e
typ s ntitie a us d in g ne liza n hie rc s
s re e e ra tio ra hie
to re re e a s s t o ins nc s o the p re e
p s nt ub e f ta e f ir a nt ntity,
c lle the s e e b w h ha a ute o
a d up rtyp , ut hic ve ttrib s r
re tio hip tha a p o tothes s t.
la ns s t p ly nly ub e

 A Re tio hip re re e a a s c tio b tw e tw o
la ns p s nts n s o ia n e e n o r
m ree
o ntitie .
s
 An e m leo are tio hipw uld b :
xa p f la ns o e
e p ye sa a s ne top je ts
m lo e re s ig d ro c
p je tsha s ta ks
ro c ve ub s
d p rtm ntsm na eo o m rep je ts
ea e a g ne r o ro c
 Re tio hip a c s ifie in te so d g e
la ns s re la s d rm f e re ,
c nne tivity, c rd lity, a e te e
o c a ina nd xis nc .

 Attrib s d s rib the e
ute e c e ntity o w h the a
f hic y re
a s c te .
s o ia d
 A p rtic r ins nc o a a uteisava .
a ula ta e f n ttrib lue
 Fo e m le "J ne R. Ha w y" is o va o the
r xa p , a tha a ne lue f
a uteNa e
ttrib m.
 The d m in o a a ute is the c lle tio o a
o a f n ttrib o c n f ll
p s ib va s a a ute c n ha . The d m in o
o s le lue n ttrib a ve o a f
Na eisac ra te s
m ha c r tring.
 Attrib sc n b c s ifie a id ntifie o d s rip rs
ute a e la s d s e rs r e c to .

 Id ntifie , m re c m o
e rs o o m nly c lle ke , uniq ly
a d ys ue
id ntify a ins nc o a e
e n ta e f n ntity.
 A d s rip r d s rib s a no
e c to e c e n-uniq c ra te tic o a
ue ha c ris f n
entity ins nc .
ta e

 Re tio hip
la ns s are c s ifie
la s d b y the ir d g e
e re ,
c nne tivity, c rd lity, d c n, typ , a e te e
o c a ina ire tio e nd xis nc .
 No a
t ll m d ling m tho o g s us a
oe e d lo ie e ll the e
s
c s ific tio .
la s a ns

 The d g e o a re tio hip is the num e o e
e re f la ns b r f ntities
a s c te w there tio hip
s o ia d ith la ns .
 Then-a re tio hip istheg ne l fo fo d g en.
ry la ns e ra rm r e re
 Sp c l c s s a the b ry, a te ry, w re the
e ia a e re ina nd rna he
d g eis2 a 3 re p c ly.
e re , nd , s e tive
 Bina ry re tio hip , the a s c tio b tw e tw
la ns s s o ia n e e n o
entitie isthem s c m o typ in there l w rld
s ot o mn e a o .
 A re urs b ry re tio hip o c w n a e
c ive ina la ns c urs he n ntity is
re te to its lf. An e m lem ht b "s m e p ye s
la d e xa p ig e o e m lo e
a m rrie to o r e p ye s
re a d the m lo e ".

 A te ry re tio hip invo s thre e
rna la ns lve e ntitie a is us d
s nd e
w n ab ry re tio hipisina e ua .
he ina la ns d q te
 Many m d ling a p a he re o nize o
oe p ro c s c g nly b ry
ina
re tio hip .
la ns s
 Te ry o n-a re tio hip a d c m o e into tw
rna r ry la ns s re e o p s d o
o m reb ry re tio hip .
r o ina la ns s

 Thec nne tivity o are tio hip d s rib sthem p ing
o c f la ns ec e ap
o a s c te e
f s o ia d ntity ins nc sin there tio hip
ta e la ns .
 Theva so c nne tivity a "o " o "m ny".
lue f o c re ne r a
 The c rd lity o a re tio hip is the a tua num e o
a ina f la ns c l br f
re te o c nc sfo e c o thetw e
la d c urre e r a h f o ntitie .
s
 Theb s typ s o c nne tivity fo re tio a : o -to
a ic e f o c r la ns re ne -
o , o -to a a m ny-to a
ne ne -m ny, nd a -m ny.
 A one-to-one (1:1) re tio hip is w n a m s o
la ns he t o t ne
ins nc o a e
ta e f ntity A is a s c te w o ins nc o
s o ia d ith ne ta e f
entity B. Fo e m le "e p ye s in the c m a a
r xa p , m lo e o p ny re
e c a s ne the o n o e Fo e c e p ye the
a h s ig d ir w ffic . r a h m lo e re
e ts a uniq o e a fo e c o e the e ts a
xis ue ffic nd r a h ffic re xis
uniq e p ye .
ue m lo e

 A one-to-many (1:N) re tio hip isw n fo o
la ns s he r ne
ins nc o e
ta e f ntity A, the a ze , o , o m ny
re re ro ne r a
ins nc so e
ta e f ntity B, b fo o ins nc o e
ut r ne ta e f ntity B,
the iso o ins nc o e
re nly ne ta e f ntity A. An e m leo a
xa p f
1:N re tio hip is
la ns s
ad p rtm nt ha m ny e p ye s
ea e s a m lo e
e c e p ye isa s ne to o d p rtm nt
a h m lo e s ig d ne e a e

 A many-to-many (M:N) re tio hip s m tim sc lle
la ns , o e e a d
no p c , isw n fo o ins nc o e
n-s e ific he r ne ta e f ntity A, the re
a ze , o , o m ny ins nc so e
re ro ne r a ta e f ntity B a fo o
nd r ne
ins nc o e
ta e f ntity B the a ze , o , o m ny
re re ro ne r a
ins nc so e
ta e f ntity A. An e m leis
xa p :
e p ye sc n b a s ne tono m retha tw
m lo e a e s ig d o n o
p je tsa thes m tim ;
ro c t a e e
p je tsm t ha a s ne a le s thre
ro c us ve s ig d t a t e
e p ye s
m lo e

 The d c n o a re tio hip ind a s the o ina
ire tio f la ns ic te rig ting
entity o ab ry re tio hip
f ina la ns .
 The entity fro w h a re tio hip o ina s is the
m hic la ns rig te
p re e
a nt ntity; the e ntity w re the re tio hip
he la ns
te ina sisthec
rm te hild entity.
 The d c n o a re tio hip is d te ine b its
ire tio f la ns e rm d y
c nne tivity.
o c
 In a o -to ne re tio hip the d c n is fro the
ne -o la ns ire tio m
ind p nd nt e
e e e ntity to ad p nd nt e
e e e ntity.

 If b th e
o ntitie a ind p nd nt, thed c n isa itra
s re e e e ire tio rb ry.
W ith o -to a re tio hip , the e
ne -m ny la ns s ntity o c
c urring
o eisthep re
nc a nt.
 Thed c n o m ny-to a re tio hip isa itra
ire tio f a -m ny la ns s rb ry.

 An id ntifying re tio hip is o in w h o o the
e la ns ne hic ne f
childentitie isa oad p nd nt e
s ls e e e ntity.
 A no e
n-id ntifying re tio hip is o in w h b th
la ns ne hic o
entitie a ind p nd nt.
s re e e e

 Exis nc d no s w the the e te e o a e
te e e te he r xis nc f n ntity
ins nc is d p nd nt up n the e te e o a the
ta e ee e o xis nc f no r,
re te , e
la d ntity ins nc .
ta e
 Thee te eo a e
xis nc f n ntity in a re tio hip is d fine a
la ns e d s
e r m nd to o o tio l.
ithe a a ry r p na
 If a ins nc o a e
n ta e f n ntity m t a a o c fo a
us lw ys c ur r n
entity to b inc e in a re tio hip the it is
e lud d la ns , n
m nd to An e m le o m nd to e te e is the
a a ry. xa p f a a ry xis nc
s te e "e ry p je t m t b m na e b a s le
ta m nt ve ro c us e a g d y ing
d p rtm nt".
ea e

 If theins nc o thee
ta e f ntity isno re uire , it iso tio l.
t q d p na
An e m le o o tio l e te e is the s te e
xa p f p na xis nc ta m nt,
"e p ye sm y b a s ne tow rk o p je ts
m lo e a e s ig d o n ro c ".

 A g ne liza n hie rc is a fo o a s c n tha
e ra tio ra hy rm f b tra tio t
s e ifie tha tw o m re e
p c s t o r o ntitie tha s re c m o
s t ha o m n
a ute c n b g ne lize into a hig r le l e
ttrib s a e e ra d he ve ntity
typ c lle as e eo g ne e
e a d up rtyp r e ric ntity.
 The lo e ve o e
w r-le l f ntitie b c m the s typ , o
s eo e ub e r
c te o s to the s e e Sub e a d p nd nt
a g rie , up rtyp . typ s re e e e
entitie .
s
 Ge ra tio o c
ne liza n c urs w n tw o m re e
he o r o ntities
re re e c te o so thes m re l-w rld o je t.
p s nt a g rie f a e a o b c

 Fo e m le W g s
r xa p , a e _Em lo e a
p ye s nd
C s ifie _Em lo e re re e c te o so thes m
la s d p ye s p s nt a g rie f a e
entity, Em lo e . In thise m le Em lo e w uld b
p ye s xa p , p ye s o e
thes e e W g s
up rtyp ; a e _Em lo e a
p ye s nd
C s ifie _Em lo e w uldb thes typ s
la s d p ye s o e ub e .
 Sub e c n b e r m
typ s a e ithe utua e lus (d jo
lly xc ive is int) or
o rla p (inc ive
ve p ing lus ).
 Amutua e lus c te o isw n a e
lly xc ive a g ry he n ntity ins nc
ta e
c n b in o o c te o
a e nly ne a g ry.
 An o rla p c te o isw n a e
ve p ing a g ry he n ntity ins nc m y
ta e a
b in tw o m re s typ s An e m le w uld b a
e o r o ub e . xa p o e
p rs n w w rks fo a unive ity c uld a o b a
e o ho o r rs o ls e
s e a tha s m unive ity.
tud nt t t a e rs

 Thec m le ne sc ns int re uire tha a ins nc s
o p te s o tra q s t ll ta e
o thes typ b re re e d in thes e e
f ub e e p s nte up rtyp .
 Ge ra tio hie rc s c n b ne te . Tha is a
ne liza n ra hie a e s d t ,
s typ o o hie rc c n b a s e e o a the
ub e f ne ra hy a e up rtyp f no r.
The le l o ne ting is lim d o b the c ns int o
ve f s ite nly y o tra f
s p ity. Sub ee
im lic typ ntitie m y b thep re e
s a e a nt ntity in a
re tio hipb no thec .
la ns ut t hild

 The is no s nd rd fo re re e
re ta a r p s nting d ta o je ts in ER
a b c
d g m . Ea h m d ling m tho o g us s its o n
ia ra s c oe e d lo y e w
no tio
ta n.
 The o ina no tio us d b C n is w e us d in
rig l ta n e y he id ly e
a a e ic te a jo
c d m s xts nd urna b ra ly s e in e r
ls ut re e n ithe
C ASE to lso p lic tio b no c d m s
o r ub a ns y n-a a e ic .
 To a the a a num e o no tio us d a o the
d y, re re b r f ta ns e ; m ng
m rec m o a Ba hm n, c w fo t, a IDEFIX.
o o m n re c a ro 's o nd
 All no tio l s s re re e e
ta na tyle p s nt ntitie a re ta ula
s s c ng r
b xe a re tio hip a line c nne tingb xe .
o s nd la ns s s s o c o s

 Ea h s
c tyle us s a s e ia s t o s b ls to re re e the
e p c l e f ym o p s nt
c rd lity o ac nne tio
a ina f o c n.

 Thes b lsus d fo theb s ER c ns tsa :
ym o e r a ic o truc re
1. Entities a re re e d b la e d re ta le . Thela e
re p s nte y b le c ng s bl
is the na e o the e
m f ntity. Entity na e s uld b
m s ho e
s ula no .
ing r uns
2 Relationships a re re e d b as lid linec nne ting
. re p s nte y o o c
tw e
o ntitie . The na e o the re tio hip is w n
s m f la ns ritte
a o theline Re tio hipna e s uld b ve s
b ve . la ns m s ho e rb .
3 Attributes, w n inc e , a lis d ins e the e
. he lud d re te id ntity
re ta le Attrib s w h a
c ng . ute hic re id ntifie
e rs a re
und rline . Attrib na e s uld b s ula no .
e d ute m s ho e ing r uns

4 Cardinality o m ny is re re e d b a line e ing in
. f a p s nte y nd
a c w fo t. If the c w fo t is o itte , the
ro 's o ro 's o m d
c rd lity iso .
a ina ne
5 Existence is re re e d b p c
. p s nte y la ing a c le o a
irc r
p rp nd ula b r o the line Ma a ry e te e is
e e ic r a n . nd to xis nc
s w b the b r (lo ks like a 1) ne to the e
ho n y a o xt ntity for
a ins nc is re uire . Op na e te e is s w b
n ta e q d tio l xis nc ho n y
p c ac lene tothee
la ing irc xt ntity tha iso tio l.
t p na

Exa p o ER No tio
m le f ta n

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