jan. 2008 yangjun chen acs-3902 1 hierarchical dbmsoutline hierarchical database management systems...

Jan. 2008 Yangjun Chen ACS-3902 1

Hierarchical DBMSOutline

Hierarchical Database Management Systems

•Hierarchical Schemas•record type•parent-child relationship•hierarchical occurrence trees•linearized form of hierarchical occurrence•Virtual parent-child relationships

•Data definition in the hierarchical model•Data manipulation language for the hierarchical model


Hierarchical DBMS

departmentdname dnumber mgrname mgrstartdate

employeename ssn bdate address

projectpname pnumber plocation

•A hierarchical schema consists of record types and PCR types.- A record is a collection of field values.- Records of the same type are grouped into record types.- A PCR type (parent-child relationship type) is a 1:N relationship

betweentwo record types.

•A hierarchical database schema consists of a number ofhierarchical schemas.

Hierarchical Schema

PCR


Hierarchical DBMS

•PCR occurrence- Each PRC occurrence relates a record of a type (e.g., a department) to

somerecords of another type (e.g., employee).

Hierarchical Schema

PCR type: PCR occurrences:

research

WongSmith Narayan

administration

Zelaya Wallace Jabbar

research

Product2Product1 Product3

administration

Computerization ...

Department

Employee

Department

Project


Hierarchical DBMS

•Properties of a Hierarchical Schema

1. One record type, called the root of the hierarchical schema, does not not participate as a child record type in any PCR type.

2. Every record type except the root participants as a child record type inexactly one PCR type.

3. A record type can participate as parent record type in any number(zero or more) of PCR types.

4. A record type that does not participate as parent record type in any PCRis called a leaf of the hierarchical schema.

5. If a record type participate as parent in more than one PCR type, then itschild record types are ordered. The order is displayed, by convention,

fromleft to right in a hierarchical diagram.

Hierarchical Schema


Hierarchical DBMS

•Hierarchical occurrenceEach hierarchical occurrence, called an occurrence tree, is atree structure whose root is a single record from some recordtype. Each subtree of the root is again a hierarchical

occurrence.

- type indicator

Hiearchical Schema




D

E

P

T S W

dependent supervisee worker


Hierarchical DBMS

- hierarchical occurrence

Hiearchical Schema

Level 1:

D AdministrationLevel 0:

Level 2:

E Zalaya E Wallace E Jabbar P computerization P new-benefit

T Abner S Zalaya S Jabbar W Wong W Zalaya W Jabbar W Zalaya


Hierarchical DBMS

- linearized form of a hierarchical occurrenceprocedure Pre_order_traversal (root_record)

beginoutput(root_record);if no child node then return;else for each child_record of root_record in left to right order

do Pre_order_traversal (child_record)

end

Hiearchical Schema

D adminitratorE ZelayaE WallaceT AbnerS ZelayaS Jabbar E JabbarP compuerizationW WongW ZelayaP new-benefitW JabbarW Zelaya


Hierarchical DBMS

•Virtual Parent-child Relationships- Problems with hierarchical model

1. M:N relationshipcauses redundancy

2. The case where a record type participates as child in more than one

PCR typecauses redundancy

3. N-ary relationships with more than two participating record typecan not be modelled

- Method dealing with the three problems:virtual record typevirtual PCR relationship

Virtual PCR


Hierarchical DBMS

•Virtual Parent-child Relationships- virtual record type

A virtual (or pointer) record type VC is a record type with the property thateach of its records contains a pointer to a record of another type VP.VC plays the role of “virtual child” and VP of ‘virtual parent” in a “virtualparent-child relationship” (VPCR).

A record of a VC type is a pointer to a record of some VP type.A record of a VP type is a “real” record.

Example: M:N relationship between Employee and Project:

Virtual PCR

Project Employee

Epointer

P

Y

E Employee Project

Ppointer

E

R

P

VC

VP


Hierarchical DBMS

•Virtual Parent-child Relationships- intersection data in a virtual record

An employee may participate in several projects. But for each project, he/she

may work for different hours per week.Therefore, the data representing “different hours per week” should beincluded in the virtual records since each pointer to an employee record

mayhave a different value. Such data are called intersection data.

- VPCRThe relationship between a virtual child and the corresponding virtual

parentis called a Virtual Parent-Child-Relationship.

Virtual PCR


Hierarchical DBMS

•Virtual Parent-child Relationships- Example:

The relationship:

Virtual PCR

ProjectABCD

Employees working on the projectE1, E3, E5E2, E4, E6E1, E4E2, E3, E4, E5

can be stored as follows:


Hierarchical DBMS

•Virtual Parent-child Relationships- Example:

Virtual PCR

A E1

E2

E3

E4

E5

E6

Ep1, 10 Ep2, 8 Ep3, 5

B

Ep4, 20 Ep5, 8 Ep6, 30

C

Ep7, 6 Ep8, 9

D

Ep10, 3 Ep11, 7 Ep12, 25Ep9, 20


Hierarchical DBMS

dependent

Dept_locations

employee

department

project

ERD for Chapter 6 database example

1

1

1

1

n

n

nn

nn

m

1

11

Works on

Virtual PCR


Hierarchical DBMS

•Virtual Parent-child Relationships- Hierarchical schema using VPCR - for a Company

database

Virtual PCR

Department

Dname Dnum

Project

Pname … ...Dlocation

Location

DemployeeEPTR

DmanagerMPTR Pworker

Hours WPTR

Employee

Ename Minit … ...

EsuperviseeSPTR

Dependent

DEPname Minit ...

D E

L P

Y

M W

S

T

StartDate


Hierarchical DBMS

•Data Definition in the Hierarchical Model- Hierarchical data definition language (HDDL)

•record typedata item of a record typekey clause

•virtual record typevirtual parent

•CHILD NUMBER clause (the left-to-right order)•ORDER BY clause

(the order of individual records of the same record type)

sequence key

Data Definition


Hierarchical DBMS

•Data Definition in the Hierarchical Model- Example

SCHEMA NAME = COMPANY

HIERARCHIES = HIERARCHY1, HIERARCHY2

RECORDNAME = EMPLOYEETYPE = ROOT OF HIERARCHY2DATA ITEMS =

FNAME CHARACTER 15MINIT CHARACTER 1LNAME CHARACTER 15SSN CHARACTER 9BDATE CHARACTER 9ADDRESS CHARACTER 30

Data Definition


Hierarchical DBMS


SEX CHARACTER 1SALARY CHARACTER 10

KEY = SSN CHARACTER 10ORDER BY LNAME, FNAME

RECORDNAME = DEPARTMENTTYPE = ROOT OF HIERARCHY1DATAITEMS =

DNAME CHARACTER 15DNUMBER INTEGER

KEY = DNAMEKEY = DNUMBERORDER BY DNAME

Data Definition


Hierarchical DBMS


RECORDNAME = DLOCATIONPARENT = DEPARTMENTCHILD NUMBER = 1DATA ITEMS =

LOCATION CHARACTER 15

RECORDNAME = DMANAGERPARENT = DEPARTMENTCHILD NUMBER = 3DATA ITEMS =

MGRSTARTDATE CHARACTER 9MPTR POINTER WITH VIRTUAL PARENT = EMPLOYEE

Data Definition


Hierarchical DBMS


RECORDNAME = PROJECTPARENT = DEPARTMENTCHILD NUMBER = 4DATA ITEMS =

PNAME CHARACTER 15PNUMBER INTEGERPLOCATION CHARACTER 15

KEY = PNAMEKEY = PNUMBERORDER BY PNAME

Data Definition


Hierarchical DBMS


RECORDNAME = PWORKERPARENT = PROJECTCHILD NUMBER = 1DATA ITEMS =

HOURS CHARACTER 4WPTR POINTER WITH VIRTUAL PARENT = EMLPOYEE

RECORDNAME = DEMPLOYEESPARENT = DEPARTMENTCHILD NUMBER = 2DATA ITEM =

EPTR POINTER WITH VIRTUAL PARENT = EMPLOYEE

Data Definition


Hierarchical DBMS


RECORDNAME = DEPENDENTPARENT = EMPLOYEECHILD NUMBER = 2DATA ITEMS =

DEPNAME CHARACTER 15SEX CHARACTER 1BIRTHDATE CHARACTER 9RELATIONSHIP CHARACTER 10

ORDER BY DESC BIRTHDATE

Data Definition


Hierarchical DBMS


RECORDNAME = ESUPERVISEEPARENT = EMPLOYEECHILD NUMBER = 1DATA ITEMS =

DEPNAME POINTER WITH IRTUAL PARENT = EMLPOYEE

Data Definition


Hierarchical DBMS

•Data Manipulation in the Hierarchical Model- Hierarchical data manipulation language (HDML)

•a record-at-a-time•HDML must be embedded in a host language such as COBOL, PL/1,Pascal, ...

user-work-area - programs•currency indicators- current of database: a single hierarchical schema and its current

database records- current of hierarchy for each hierarchical schema- current of record type for each record type•command classification- retrieval: GET- record update: INSERT, DELETE, REPLACE- current record: GET HOLD

Data Manipulation


Hierarchical DBMS

•Data Manipulation in the Hierarchical Model- GET

•GET FIRST <record type name> [WHERE <condition>]•GET NEXT <record type name> [WHERE <condition>]

$GET FIRST EMPLOYEE WHERE SALARY < ‘20000.00’;while DB_STATUS = 0 do

beginwriteln (P_EMPLOYEE.FNAME,

P_EMPLOYEE.LNMAE);$GET NEXT EMPLOYEE WHERE SALARY <

‘20000.00’end

Data Manipulation


Hierarchical DBMS


• GET (FIRST | NEXT) PATH <hierarchical path> [WHERE <condition>]

$GET FIRST PATH EMPLOYEE, DEPENDENT WHERE EMPLOYEE.FNAME=‘John’ AND

DEPENDENT.DEPNAME=‘John’;while DB_STATUS = 0 do

beginwriteln (P_EMPLOYEE.LNAME,

P_EMPLOYEE.BDATE,P_DEPENDENT.BIRTHDATE);

$GET NEXT PATH EMPLOYEE, DEPENDENTWHERE EMPLOYEE.FNAME=‘John’ AND

DEPENDENT.DEPNAME=‘John’end

Data Manipulation


Hierarchical DBMS


• GET NEXT <child record type name>WITHIN [VIRTUAL] PARENT [<parent record type

name] [WHERE <condition>]

$GET FIRST PATH DEPARTMENT, PROJECT WHERE DEPARTMENT.DNAME=‘Research’;

while DB_STATUS = 0 dobeginwriteln (P_PROJECT.PNAME);$GET NEXT PROJECT WITHIN PARENTend;

Data Manipulation


Hierarchical DBMS

•Data Manipulation in the Hierarchical Model- Calculating aggregate functions: COUNT, AVERAGE, ...

$GET FIRST PATH DEPARTMENT, DEMPLOYEE;while DB_STATUS = 0 do

begintotal_sal :=0; no_of_emps :=0;writeln (P_DEPARTMENT.DNAME);while DB_STATUS = 0 do

begin$GET VIRTUAL PARENT EMPLOYEE;total_sal := total_sal + conv_sal(P_EMPLOYEE.SALARY);no_of_emps := no_of_emps +1; $GET NEXT DEMPLOYEES WITHIN PARENT

DEPARTMENTend writeln (‘no of emps =’, no_of_emps, ‘avg sal of emps =’,

total_sal/no_of_emps);$GET NEXT PATH DEPARTMENT, DEMPLOYEES

end;

Data Manipulation


Hierarchical DBMS

•Data Manipulation in the Hierarchical Model- Update: INSERT, DELETE, REPLACE

P_EMPLOYEE.FNAME := ‘John’;P_EMPLOYEE.LNAME := ‘Smith’; P_EMPLOYEE.MINIT := ‘F’;P_EMPLOYEE.SSN := ‘567875432’; P_EMPLOYEE.ADDRESS := ‘40 N.W. 80TH ...’; P_EMPLOYEE.BDATE := ‘10-Jan-55’; P_EMPLOYEE.SEX := ‘M’; P_EMPLOYEE.SALARY := ‘30000.00’; $INSERT EMPLOYEE FROM P_EMPLOYEE;

Data Manipulation


Hierarchical DBMS


$GET HOLD FIRST EMPLOYEE WHERE SEX = ‘M’; while DB_STATUS = 0 do

beginwriteln (P_EMPLOYEE.LNAME,

P_EMPLOYEE.FNAME);$DELETE EMPLOYEE$GET HOLD NEXT EMPLOYEE WHERE SEX =

‘M’end;

Data Manipulation


Hierarchical DBMS


$GET FIRST PATH DEPARTMENT, DEMPLOYEEWHERE DNAME = ‘Reseach’; while DB_STATUS = 0 do

begin$GET HOLD VIRTUAL PARENT EMPLOYEE OF

DEMPLOYEESP_EMPLOYEE.SALARY := P_EMPLOYEE.SALARY * 1.1;$REPLACE EMPLOYEE FROM P_EMPLOYEE$GET NEXT DEMPLOYEES WHERE PARENT

DEPARTMENTend;

Data Manipulation


Hierarchical DBMSParent/child relationships




Two parent/child relationships are in the above schema:

•department/employee

•department/project


Hierarchical DBMS




Using the data we had previously seen in Ch 7, we can depict the following 3 instances of department/employee:

Research

Smith Wong Narayan English

Administration

Zelaya Wallace Jabbar

Headquarters

Borg

Parent/child instances


Hierarchical DBMS




Using the data we had previously seen in Ch 7, we can depict the following 3 instances of department/project:

ProductX ProductY ProductZComputerization Newbenefits

ReorganizationAdministration

ResearchHeadquarters

Parent/child instances


Hierarchical DBMS

ComputerizationNewbenefits

Reorganization

Administration

Research

Headquarters

SmithWong

NarayanEnglish

ZelayaWallace

Jabbar

Borg

In the following 3 hierarchical records are depicted. This is another way that such information is often depicted in practice.

Hierarchical records

ProductXProductY

ProductZ

Note that a child record cannot exist without its parent record - this is similar to the concepts of

•FK integrity and •weak entity


Hierarchical DBMS

Schema name = companyrecord

name=department field dname character 15 field dnumber integer field mgrname character 30 field mgrstartdate datekey=dnumber

recordname=employeeparent=department field name character 15 field ssn character 9 field bdate date field address character 30key=ssn

recordname=projectparent=department field pname character 15 field pnumber integer field location character 15key=pnumber

Schema definition

Need:

Names of records

parent/child relationships

fields

keys

syntax will vary, but these are the types of things that must be present.


Hierarchical DBMSData manipulation

Navigational - not set-oriented - you retrieve one record at a time

Retrieval

GU, Get unique

GN, Get next

GNP, Get next within parent

Updating

ISRT, Insert

DLET, Delete

REPL, Replace

retrieve a specific record

using your current position, get the next record in the database

using your current position, get the next child record for that parent

GU

, GN

, GN

P, ISR

T, D

LE

T, R

EP

L are

IMS com

mand nam

es


Hierarchical DBMS

ProductXProductY

ProductZ

ComputerizationNewbenefits

Reorganization

Administration

ResearchHeadquarters

SmithWong

NarayanEnglish

ZelayaWallace

Jabbar

Borg

Consider the database

Navigating through the database

GU Department (dname=headquarters)Loop

GNPexit when status code = ????

End Loop

Program would retrieve the Department record and all of its dependents

jan. 2008 yangjun chen acs-3902 1 hierarchical dbmsoutline hierarchical database management systems...

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