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E4161 : SISTEM KOMPUTER & APLIKASI. UNIT 13 – REKABENTUK MODEL PANGKALAN DATA RANGKAIAN. PANGKALAN DATA RANGKAIAN. Diperkenalkan sebagai penambahbaikan kepada model pangkalan data hierarki . Set – hubungan antara rekod ahli dengan satu atau lebih bapa ( pemilik ).

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e4161 sistem komputer aplikasi

E4161 : SISTEM KOMPUTER & APLIKASI

UNIT 13 – REKABENTUK MODEL PANGKALAN DATA RANGKAIAN

pangkalan data rangkaian
PANGKALAN DATA RANGKAIAN
  • Diperkenalkansebagaipenambahbaikankepada model pangkalan data hierarki.
  • Set – hubunganantararekodahlidengansatuataulebihbapa (pemilik).
  • Rekod – SALESREP, CUSTOMER, PRODUCT…
  • Pemilik – PRODUCT, INVOICE, PAYMENT…
pangkalan data rangkaian1
PANGKALAN DATA RANGKAIAN
  • Ciri-ciri
    • Model rangkaianlebihfleksibelkeranamaklumatbolehdiperolehimelaluibanyakcara.
    • Model rangkaianbolehmewakilijenishubunganbanyakkebanyak (M:M)
    • Setiappemiliktidakterhadkepadahubungansatuarahsahajadansetiaprekodbolehmempunyailebihdarisatuhubungan.
    • Setiaphubunganantararekodahlidanpemilikadalahmelaluipetunjuk.
pangkalan data rangkaian2
PANGKALAN DATA RANGKAIAN
  • Struktur :
    • Rekod
    • Jenisrekod
    • Item data
pangkalan data rangkaian3
PANGKALAN DATA RANGKAIAN
  • Jenis set – peneranganhubunganantaraduajenisrekod (1:M)
  • Jenis set mempunyai 3 elemen:
    • Namauntukjenis set
    • Jenisrekodpemilik
    • Jenisrekodahli
pangkalan data rangkaian4
PANGKALAN DATA RANGKAIAN
  • Kejadian set – dibinaolehsaturekodpemilikdanbeberaparekodahlidarijenisrekodahli.
database management system by r panneerselvam
DATABASE 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 MANUAL
    • This 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.
database management system by r panneerselvam1
DATABASE MANAGEMENT SYSTEM BY R. PANNEERSELVAM
  • RETENTION means holding the association of member records with their respective owner records.
  • RETENTION IS FIXED
    • This means that the member records of a set are permanently associated with their owner records of that set.
  • RETENTION IS MANDATORY
    • The 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.
database management system by r panneerselvam2
DATABASE 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.
  • ORDER
  • CHECK
  • SET SELECTION
library database1
LIBRARY DATABASE

publish set

T-A set

checkout set

A-T set

vchkout set

collection set

history set

subskima ddl
SUBSKIMA DDL

checkout set

vchkout set

collection set

history set

slide19
DML
  • 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
slide20
DML
  • 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 record
    • RECONNECT : combines the function of DISCONNECT and CONNECT
    • ERASE : 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.