Rancangan Basis Data

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)

N M

4/20/2007 Fathur'2011

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)

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

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

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, 3.5 999-31-2356, jzhang@, Jie Zhang, 20, 3.0 999-32-1234, ajain@, Anil Jain, 21, 3.8

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

4/20/2007 Fathur'2011

Jenis Attribute

• Composite vs Simple(atomic) Attributes • Single-valued vs Multivalued Attributes • Stored vs Derived Attributes

• Null values

• Complex Attributes • Key Attribute

4/20/2007 Fathur'2011

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

4/20/2007 Fathur'2011

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

4/20/2007 Fathur'2011 Id_B(pk) -dt_B -id_A(FK ) Id_A(pk) - dt_A 1 1 A C B Id_A(fk) Id_B(fk) Id_B(pk) dt_B -Id_B(fk) Id_A(pk) - dt_A M 1 A C B Id_A(fk) Id_B(fk) Id_B(pk) - dt_B Id_A(pk) - dt_A N M A C B Id_A(fk) Id_B(fk) - Dt_C

4/20/2007 Fathur'2011 KdKul (PK) NamaKul sks NIM (FK) KdKul (FK) Nilai NIM (PK) Nama Alamat N M Mahaiswa

ambil 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 ?

4/20/2007 Fathur'2011 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 M 1 Pegawai Isi Absensi - tglBayar - Jum_Angsur * NoPinj * NoPinj - tgl - jum - ferk N M Pinjaman angsu r Angsuran

4/20/2007 Fathur'2011 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 N M Anggota pinja m Buku Kembal i Denda N

4/20/2007 Fathur'2011 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 - Nama Pegawai Is A Tetap Honorer

4/20/2007 Fathur'2011 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

4/20/2007 Fathur'2011

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 handles Class

A Lecturer may handle zeroor many classes.

A class is handled by one and only one Lecturer.

(0,N) (1,1) Lecturer Class (0,N) (1,1) handles 1 M