Date post: | 13-Apr-2018 |
Category: |
Documents |
Upload: | don-seneca |
View: | 216 times |
Download: | 0 times |
of 44
7/26/2019 Chapter 04 Database Learning Skills
1/44
Introduction to
DatabasesChapter 4:Designing aDatabase
7/26/2019 Chapter 04 Database Learning Skills
2/44
Designing Relational
TablesTypical process for converting E-Rdiagrams to relational tables: Each entity converts to table
For many-to-many relationships, each
associative entity converts to table Attribtes become table colmns
Ensre foreign !eys appear in proper placesin tables
To convert single entity, create table ofsame name "ith colmn for eachattribte
7/26/2019 Chapter 04 Database Learning Skills
3/44
Salesperson Entity and
Table
7/26/2019 Chapter 04 Database Learning Skills
4/44
Converting Binary
Relationships #reater importance in selectingidenti$er and primary !ey
%denti$er and primary !ey de$ne foreign
!ey that establishes relationshipsbet"een tables
&ften more than one "ay torepresent entity relationships as
relational tables
7/26/2019 Chapter 04 Database Learning Skills
5/44
Example: Converting ! BinaryRelationship
7/26/2019 Chapter 04 Database Learning Skills
6/44
Example: Converting ! BinaryRelationship
7/26/2019 Chapter 04 Database Learning Skills
7/44
Example: Converting ! Binary Relationship
7/26/2019 Chapter 04 Database Learning Skills
8/44
Example: Converting ! BinaryRelationship
'onverting one-to-one(alesperson)&*ce relationship
&ptions:
'onvert relationship tosingle)combined table
'onvert relationship to t"o tables
7/26/2019 Chapter 04 Database Learning Skills
9/44
Example: Converting ! BinaryRelationship
'onsiderations: +siness environment considers
(alesperson and &*ce as separateentities
odality of ero at (alesperson entity inE-R diagram .o*ce may have no oneassigned/
(alesperson entity in E-R diagram has
relationships "ith other entities
7/26/2019 Chapter 04 Database Learning Skills
10/44
Example: Converting ! BinaryRelationship
(oltion 0:
'ombine t"o entities into one table
7/26/2019 Chapter 04 Database Learning Skills
11/44
Example: Converting ! BinaryRelationship
(oltion 1: T"o separate tables &*ce 2mber as foreign !ey in
(alesperson table
7/26/2019 Chapter 04 Database Learning Skills
12/44
Example: Converting ! BinaryRelationship
(oltion 3:
T"o separate tables
(alesperson 2mber as foreign !ey in
&*ce table
7/26/2019 Chapter 04 Database Learning Skills
13/44
Example: Converting !" BinaryRelationship
7/26/2019 Chapter 04 Database Learning Skills
14/44
Example: Converting !" BinaryRelationship
Each occrrence of (alesperson isrelated to ero or more occrrencesof 'stomer
4ni5e identi$er of entity on 6one7side is placed as foreign !ey in entityof 6many7 side
7/26/2019 Chapter 04 Database Learning Skills
15/44
Example: Converting !" BinaryRelationship
7/26/2019 Chapter 04 Database Learning Skills
16/44
Example: Converting "!" BinaryRelationship
7/26/2019 Chapter 04 Database Learning Skills
17/44
Example: Converting "!" BinaryRelationship
ost relational D+( systems do notdirectly spport many-to-manyrelationships
(oltion: %nclde associative entity toestablish relationship
ay se composite !ey as primary!ey in associative entity
7/26/2019 Chapter 04 Database Learning Skills
18/44
Example: Converting "!" BinaryRelationship
7/26/2019 Chapter 04 Database Learning Skills
19/44
Example: Converting "!" BinaryRelationship
7/26/2019 Chapter 04 Database Learning Skills
20/44
Example: Converting ! #naryRelationship
7/26/2019 Chapter 04 Database Learning Skills
21/44
Example: Converting ! #naryRelationship
8ith:
&nly one entity type involved, and
&ne-to-one relationship
'onversion re5ires only one table
7/26/2019 Chapter 04 Database Learning Skills
22/44
Example: Converting !" #naryRelationship
7/26/2019 Chapter 04 Database Learning Skills
23/44
Example: Converting !" #naryRelationship
7/26/2019 Chapter 04 Database Learning Skills
24/44
Example: Converting "!" #naryRelationship
any-to-many nary relationship:
For e9ample: one prodct can beconstrcted ot of set or sbset of otherprodcts
#eneral rle in conversion: 2mber of tables e5al to nmber of entity
types pls one more table for many-to-manyrelationship
- nary relationship - 1 tables - binary relationship - 3 tables
- ternary relationship - for tables
7/26/2019 Chapter 04 Database Learning Skills
25/44
Example: Converting "!" #naryRelationship
7/26/2019 Chapter 04 Database Learning Skills
26/44
Example: Converting "!" #naryRelationship
7/26/2019 Chapter 04 Database Learning Skills
27/44
Example: $ood ReadingBoo%stores
7/26/2019 Chapter 04 Database Learning Skills
28/44
Example: $ood ReadingBoo%stores
7/26/2019 Chapter 04 Database Learning Skills
29/44
Example: $ood ReadingBoo%stores
7/26/2019 Chapter 04 Database Learning Skills
30/44
&ormali'ing Data
Data normaliation:ethodology fororganiing attribtes into tables toeliminate redndancy among non!ey
attribtes #oals:
Each resltant table describes single entitytype or single many-to-many relationship
Foreign !eys appear e9actly "here needed ;roperly strctred relational database
7/26/2019 Chapter 04 Database Learning Skills
31/44
&ormali'ation
Techni(ues T"o types of inpt needed for datanormaliation process
0< =ist of all attribtes to be incorporated indatabase, inclding intersection data attribtes
1< =ist of fnctional dependencies: all de$ningassociations bet"een attribtes
%n fnctional dependencies, oneattribte .determinate attribte/
de$nes vale of another attribte(alesperson 2mber > (alesperson 2ame
7/26/2019 Chapter 04 Database Learning Skills
32/44
Salesperson Entity )ttributes
7/26/2019 Chapter 04 Database Learning Skills
33/44
Salesperson Entity *unctional Dependencies
7/26/2019 Chapter 04 Database Learning Skills
34/44
Example: De+ning )ttributes and *unctionalDependencies
?antity is de$ned by t"o combinedattribtes
anager is de$ned independently by
t"o attribtes Department 2mber and (alesperson
2mber
(alesperson 2mber also de$nes
Department 2mber
7/26/2019 Chapter 04 Database Learning Skills
35/44
&ormali'ing Data
2ormal forms: Rles for data normaliation
Three main normal forms First normal form
(econd normal form
Third normal form 2ormaliation:
4ses normal forms to step throgh 6decompositionprocess7 that decomposes attribtes into sbgrops
%n third normal form, grop of tables is
"ell-strctred relational database "ith nodata redndancy
7/26/2019 Chapter 04 Database Learning Skills
36/44
&ormali'ing Data
First normal form: Eliminates mltiple vales
(econd normal form: Eliminates partial ,unctional dependencies
.data dependent on part of primary !ey/
Every non!ey attribte mst be fllyfnctionally dependent on entire !ey of table
Third normal form: Eliminates transitive dependencies .one
non!ey attribte is fnctionally dependent onanother/
2on!ey attribtes are not allo"ed to de$neother non!ey attribtes
7/26/2019 Chapter 04 Database Learning Skills
37/44
Example: #nnormali'ed
Data
7/26/2019 Chapter 04 Database Learning Skills
38/44
*irst &ormal *orm
7/26/2019 Chapter 04 Database Learning Skills
39/44
Second &ormal *orm
7/26/2019 Chapter 04 Database Learning Skills
40/44
Third &ormal *orm
7/26/2019 Chapter 04 Database Learning Skills
41/44
Denormali'ing Data
Denormaliing may be needed "hen:
2ormaliation has been ta!en to e9tremeToo many small tables creating more "or! and
storage space
E
7/26/2019 Chapter 04 Database Learning Skills
42/44
Summary
%n converting E-R diagrams to relationaltables, each entity typically converted intotable, "ith attribtes as table colmns