UNIT 13 REKABENTUK MODEL PANGKALAN DATA RANGKAIAN PANGKALAN DATA RANGKAIAN Diperkenalkan sebagai penambahbaikan kepada model pangkalan data hierarki Set hubungan ID: 800639
Download The PPT/PDF document "E4161 : SISTEM KOMPUTER & APLIKASI" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
E4161 : SISTEM KOMPUTER & APLIKASI
UNIT 13 – REKABENTUK MODEL PANGKALAN DATA RANGKAIAN
Slide2PANGKALAN DATA RANGKAIAN
Diperkenalkan
sebagai penambahbaikan kepada model pangkalan data hierarki.Set – hubungan antara rekod ahli dengan satu atau lebih bapa (pemilik).Rekod – SALESREP, CUSTOMER, PRODUCT…Pemilik – PRODUCT, INVOICE, PAYMENT…
Slide3PANGKALAN DATA RANGKAIAN
Ciri-ciri
Model
rangkaian lebih fleksibel kerana maklumat boleh diperolehi melalui banyak cara.Model rangkaian boleh mewakili jenis hubungan banyak ke banyak (M:M)Setiap pemilik tidak terhad kepada
hubungan
satu
arah
sahaja
dan
setiap
rekod
boleh
mempunyai
lebih
dari
satu
hubungan
.
Setiap
hubungan
antara
rekod
ahli
dan
pemilik
adalah
melalui
petunjuk
.
Slide4PANGKALAN DATA RANGKAIAN
Struktur
:
RekodJenis rekodItem data
Slide5PANGKALAN DATA RANGKAIAN
Jenis
set –
penerangan hubungan antara dua jenis rekod (1:M)Jenis set mempunyai 3 elemen:Nama untuk jenis setJenis rekod pemilikJenis rekod ahli
Slide6PANGKALAN DATA RANGKAIAN
Kejadian
set –
dibina oleh satu rekod pemilik dan beberapa rekod ahli dari jenis rekod ahli.
Slide7DATABASE MANAGEMENT SYSTEM BY R. PANNEERSELVAM
INSERTION IS AUTOMATIC
This means that if a member record is inserted in its record type, then it will be automatically connected to its associated owner record. One can use this type of insertion if the member records are to be permanently connected to their owner records for a longer period.
INSERTION IS MANUALThis implies that if a member is inserted in its record type, then it will be connected to its associated owner record using an explicit program. This type of insertion can be used if the ownership of member records changes very often.
Slide8DATABASE MANAGEMENT SYSTEM BY R. PANNEERSELVAM
RETENTION
means holding the association of member records with their respective owner records.
RETENTION IS FIXEDThis means that the member records of a set are permanently associated with their owner records of that set.RETENTION IS MANDATORYThe member records of a set are temporarily connected to their owner records of that set. This means that a given member record will keep changing its owner from time to time.While changing the ownership of a member record, one can use any one of the following options:DISCONNECT a member record from the present owner and then CONNECT it to a new owner.RECONNECT the owner of a member record in single command.
Slide9DATABASE MANAGEMENT SYSTEM BY R. PANNEERSELVAM
RETENTION IS OPTIONAL
This type of retention permits the user to remove the association of owner records to their member records and leave its member records unconnected to some other owner records until told to do so by some user program.
ORDERCHECKSET SELECTION
Slide10LIBRARY DATABASE
Slide11SKIMA DDL
Slide12Slide13Slide14Slide15Slide16LIBRARY DATABASE
publish set
A-T set
T-A setcollection setcheckout setvchkout sethistory set
Slide17SUBSKIMA DDL
collection set
checkout set
vchkout
set
history set
Slide18Slide19DML
Retrieval commands:
FIND : used to locate a record in a given file of the database.
GET : used to transfer the content of the located record into the working area.OBTAIN : an improved command to combine the functions of FIND and GET commands
Slide20DML
Modification commands:
STORE : include a new record into a database and connects it to all the sets in which the record is an automatic member.
MODIFY : update the contents of an existing record.CONNECT : links a specific member record of a set which is currently located to its owner record.DISCONNECT : delinks a currently located member record of a set from its owner recordRECONNECT : combines the function of DISCONNECT and CONNECTERASE : remove a record in a file of the database, disconnect it from its owner and remove all the records of member to which it is the owner.