sistem basis data - fathur's...
TRANSCRIPT
4/20/2007 Fathur'2011
Berisikan pemodelan data yang tertuang dalam analisa data beserta relasi yang ada dalam bentuk ERD yang diusulkan Peter P.Chen, CDM hanya memperlihatkan item-item sebagai berikut :
- Entiti
- Relasi
- Kardinalitas
Rancangan Basis Data
1. Context Data Model (CDM)
NMMahaiswa Isi KRSNM
Pilih Matakuliah
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Pemodelan Data :Entity Relationship Diagram (ERD)/Diagram Hubungan Entitas (DHE)
Fungsi : - memodelkan data
- melihat data yang akan disimpan
Simbol-simbol :
: - Entity Set/objek data
- Kata benda
Contoh : mahasiswa, pelanggan, barang, dan lain-lain
: - Relationship/hubungan
- Menghubungan entity set
- Kata kerja
contoh : kerja, ambil, isi, dan lain-lain
Atribut : Ciri dari sebuah entity
Cardinality : - tingkat hubungan
- melihat tingkat hubungan suatu relationship
1 : M (hubungan satu ke banyak)
M : N (hubungan banyak ke banyak)
1 : 1 (hubungan satu ke satu)
Tidak boleh ada hubungan antar relationship
The Entity Relationship (ER)
Model• ER Modeling is a top-down approach to database
design.
• Entity Relationship (ER) Diagram
– A detailed, logical representation of the entities,
associations and data elements for an
organization or business
• ERD represents the conceptual database as viewed
by end user
• ERDs depict the ER model’s three main components:
– Entities
– Attributes
– Relationships
Entity-Relationship (ER) Modeling.
• ER Modeling is a top-down approach to
database design.
• Entity Relationship (ER) Diagram
– A detailed, logical representation of the entities,
associations and data elements for an organization or
business
• Notation uses three main constructs
– Data entities
– Relationships
– Attributes
Chen Model &
Crow’s Foot
Model
Person, place, object, event
or concept about which data
is to be maintained
named property or
characteristic of an
entity
Association
between the
instances of one or
more entity types
Represents a set or collection of
objects in the real world that
share the same properties
Chen Notation
EntityName Verb Phrase AttributeName
Entities
• Refers to the entity set and not to a
single entity occurrence
• Corresponds to a table and not to a row
in the relational environment
• In both the Chen and Crow’s Foot
models, an entity is represented by a
rectangle containing the entity’s name
• Entity name, a noun, is usually written in
capital letters
Entity vs. Entity Set (Entities)
Entity Set (Entities) --- Student
John Smith (999-21-3415, jsmith@, John Smith, 18, 3.5)
Students in ITCS3160
999-21-3415, jsmith@, John Smith, 18, 3.5999-31-2356, jzhang@, Jie Zhang, 20, 3.0999-32-1234, ajain@, Anil Jain, 21, 3.8
entity
Is it an entity?
Rules:
1. An entity must be important to the organisation.
2. An entity must have at least one attribute.
3. An entity must occur more than once (there must be more than one customer)
4. Each entity occurrence (record) must be uniquely identifiable (customer id)
Entities
• Examples of entities:– Person: EMPLOYEE, STUDENT, PATIENT
– Place: STORE, WAREHOUSE
– Object: MACHINE, PRODUCT, CAR
– Event: SALE,REGISTRATION, RENEWAL
– Concept: ACCOUNT, COURSE
• Guidelines for naming and defining entity types:– An entity type name is a singular noun
– An entity type should be descriptive and specific
– An entity name should be concise
– Event entity types should be named for the result of the event, not
the activity or process of the event.
Attributes
• Characteristics of entities
• In Chen model, attributes are
represented by ovals and are connected
to the entity rectangle with a line
• Each oval contains the name of the
attribute it represents
• In the Crow’s Foot model, the attributes
are simply written in the attribute box
below the entity rectangle
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Jenis Attribute
• Composite vs Simple(atomic) Attributes
• Single-valued vs Multivalued Attributes
• Stored vs Derived Attributes
• Null values
• Complex Attributes
• Key Attribute
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Composite vs Simple (Atomic)
• Composite attributes dapat dibagi ke subbagian yang lebih
kecil dan merepresentasikan attribute yang lebih dasar
• Simple attributes tidak dapat dibagi
• Contoh: Alamat -> Jalan, Kota, Propinsi,KodePos, Negara;
Jalan -> NoRumah, NamaJalan
Single-valued vs Multivalued Attributes
• umur -> single-valued
• noTelpon -> multivalued
Store vs Derived Attributes
• umur -> derived attribute dari tglLahir
• tglLahir -> stored attribute
Null values
• noTelpon -> null (jika tidak punya telpon)
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Relationship
• Manager yang mengelola suatu Department ->
hubungan antara Employee dengan Department; manages
• Department yang mengontrol suatu Project ->
hubungan antara entity Department dengan Project; controls
• Employee yang bekerja pada Department tertentu ->
hubungan antara entity Employee dengan Department;
works_for
• Cardinality Ratios untuk relationship biner menggambarkan
jumlah instances suatu entity dapat berpartisipasi
Contoh: works_for;
DEPARTMENT:EMPLOYEE = 1:N
Kemungkinan cardinality ratios: 1:1, 1:N, N:1, M:N
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Id_B(pk)
-dt_B
-id_A(FK
)
Id_A(pk)
- dt_A
11AC
B
Id_A(fk)
Id_B(fk)
Id_B(pk)
dt_B
-Id_B(fk)
Id_A(pk)
- dt_A
M1AC
B
Id_A(fk)
Id_B(fk)
Id_B(pk)
- dt_B
Id_A(pk)
- dt_A
NMAC
B
Id_A(fk)
Id_B(fk)
- Dt_C
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KdKul (PK)
NamaKul
sks
NIM (FK)
KdKul (FK)
Nilai
NIM (PK)
Nama
Alamat
NMMahaiswaambil
Mata kuliah
contoh :
1. Dalam sistem perkuliahan, seorang mahasiswa dapat mengambil lebih
dari satu mata kuliah, dan 1 mata kuliah dapat diambil oleh lebih 1
mahasiswa.
ERD-nya adalah :
2. Dalam sistem kepegawaian, jika asumsi seorang pegawai dapat
memegang lebih dari satu jabatan dan satu jabatan hanya dapat
dipegang oleh satu pegawai, maka ERD-nya adalah ?
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1. Weak Entity (Entitas lemah)
Terjadi bila sebuah entity tidak memiliki primary key bergantung pada strong key
Contoh :
Jenis-Jenis Entitas :
- tanggal
- jum_masuk
- jum_keluar
* NIP
- Nama
- Alamat
M1PegawaiIsi
Absensi
- tglBayar
- Jum_Angsur* NoPinj
* NoPinj
- tgl
- jum
- ferk
NMPinjamanangsu
r
Angsuran
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2. Agregation (Agregasi)
Terjadi bila dua buah entiti yang berlesai akan direlasikan ke entiti lain.
Contoh ;
Jenis-Jenis Entitas :
* Noang
* NoBuku
* Kd_Denda
- Jumlah
* Kd_Denda
- Jenis
M
* NoBuku
- Judul* Noang
* NoBuku
* Noang
- Nama
- Alamat
NMAnggotapinja
m
Buku
Kembal
i
Denda
N
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3. Spesialisasi dan Generalisasi (Is A)
Terjadi bila terdapat beberpa atribut pada beberapa entiti dengan Primary Key (PK)
yang sama.
Contoh :
Jenis-Jenis Entitas :
- Nama
- Edisi
- Harga
- Judul
- NRP
- Judul
- Pengarang
- Harga
*
No_Koleksi
- Tgl_Beli
Koleksi
Is A
Buku Skripsi Majalah
- Upah_Hari
- UpahLembur
- GajiPokok
- t_anak
- t_sehat
* NIP
- NamaPegawai
Is A
Tetap Honorer
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KRS
NoKrs (PK1) (FK)
NIM (PK2) (FK)
ThAkad
Semester
StatusStudi
Berisikan ERD yang didasarkan pada CDM yang ada. LDM menggunakan notasi ERD yang diusulkan oleh James Martin atau dikenal dengan notasi Informastion Engineering. Bentuk LDM ini sudah menyertakan item-item berikut :
- Entiti
- Kardinalitas
- Atribut-atribut key dan non key
- Transformasi kardinalitas Many-to-Many dalam CDM ke dalam bentuk
Associative Entity
2. Logical Data Model (LDM)
MHS
NIM (PK)
Nama
Alamat
TmpLahir
TglLahir
KdJurusan
ThnMasuk
Status
PilihMK
NoKRS (PK1)(FK)
KodeMK (PK2)(FK)
StatusUlang
HMutu
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Notasi LDM
• Chen Model
– 1 to represent one.
– M to represent many
• Crow’s Foot
many
One
One or many
1
M
Zero or many
One or one
Zero
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Lecturer Classhandles
A Lecturer may handle zero or many classes.
A class is handled by one and only one Lecturer.
(0,N)(1,1)
Lecturer Class
(0,N) (1,1)
handles1
M