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№1 слайд![Lecture . Network Data Model](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img0.jpg)
Содержание слайда: Lecture 4. Network Data Model
National Aviation University
Computer Science Faculty
Department of Software Engineering
№2 слайд![CONTENTS Brief history](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img1.jpg)
Содержание слайда: CONTENTS
Brief history
Network data structure
Network data structure operations
Integrity constraints
Advantages and drawbacks
№3 слайд![Brief history](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img2.jpg)
Содержание слайда: Brief history
№4 слайд![Fields and record types](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img3.jpg)
Содержание слайда: Fields and record types
Graphic notation:
№5 слайд![Keys](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img4.jpg)
№6 слайд![Set type and instance](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img5.jpg)
Содержание слайда: Set type and instance (occurrence)
Set owner. There is only one set owner record
Set members. There may be 0, 1 or more set member records.
№7 слайд![Example of the set type and](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img6.jpg)
Содержание слайда: Example of the set type and instance
№8 слайд![Multilevel Hierarchy](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img7.jpg)
Содержание слайда: Multilevel Hierarchy
№9 слайд![Representation of m n](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img8.jpg)
Содержание слайда: Representation of m:n relationships
№10 слайд![Schema and instance of m n](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img9.jpg)
Содержание слайда: Schema and instance of m:n relationships
№11 слайд![Cycles and loops](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img10.jpg)
Содержание слайда: Cycles and loops
№12 слайд![Possible categories of](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img11.jpg)
Содержание слайда: Possible categories of network schemas
№13 слайд![Application and DBMS User](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img12.jpg)
Содержание слайда: Application and DBMS
User Work Area (UWA) contains:
current state indicators,
records,
error status.
№14 слайд![Network data model operations](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img13.jpg)
Содержание слайда: Network data model operations
Data selection (Query Language - QL):
FIND - locates a described record occurrence
GET - reads a record occurrence from the database
Data manipulation (Data Manipulation Language-DML):
STORE - puts a record occurrence into the database
INSERT - inserts member record into a set occurrence
REMOVE - removes member record from a set occurrence
DELETE - deletes current record from DB
MODIFY - updates current record
№15 слайд![Data searching and selection](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img14.jpg)
Содержание слайда: Data searching and selection
№16 слайд![Fine the record by DB-key](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img15.jpg)
Содержание слайда: Fine the record by DB-key
№17 слайд![Fine the record by field](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img16.jpg)
Содержание слайда: Fine the record by field values
№18 слайд![Scanning a Set Occurrence](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img17.jpg)
Содержание слайда: Scanning a Set Occurrence
№19 слайд![The next member record in the](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img18.jpg)
Содержание слайда: The next member record in the set occurrence
№20 слайд![The prior member record in](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img19.jpg)
Содержание слайда: The prior member record in the set occurrence
№21 слайд![The first and the last member](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img20.jpg)
Содержание слайда: The first and the last member record in
the set occurrence
№22 слайд![Location of the owner record](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img21.jpg)
Содержание слайда: Location of the owner record of the
current set occurence
№23 слайд![Example](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img22.jpg)
Содержание слайда: Example
№24 слайд![Put a record occurrence into](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img23.jpg)
Содержание слайда: Put a record occurrence into the database
create a record occurrence in UWA;
execute the command STORE.
№25 слайд![Attaching record occurrence](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img24.jpg)
Содержание слайда: Attaching record occurrence from DB
to the set occurrence
Make required set occurrence the current of set type
Make inserted record occurrence the current one
Execute the command INSERT
№26 слайд![Remove a record occurrence of](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img25.jpg)
Содержание слайда: Remove a record occurrence of a certain
type from a certain set occurrence
Make designated record be the current one
Execute the command REMOVE
№27 слайд![Updating record occurrence](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img26.jpg)
Содержание слайда: Updating record occurrence
The MODIFY command copies values from a record in
UWA into the current record occurrence of the DB.
№28 слайд![Deleting record occurrence](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img27.jpg)
Содержание слайда: Deleting record occurrence from DB
The DELETE command removes from DB the current
record occurrence
The set owner may be deleted when this set do not
contains member records
№29 слайд![Advantages and drawbacks The](/documents_5/94ab0e54b704c3942e1dbad2e2f295d5/img28.jpg)
Содержание слайда: Advantages and drawbacks
The network data model basically has the same
advantages and drawbacks as hierarchical data
model.
The only basic difference of the network data
model in comparison with hierarchical data model
is the opportunity to represent many-to-many
relationships.