Distributed Database Design

Distributed Database Design

COSC 5040Week One

Jiangping WangWebster University Distributed Database Design

OutlineIntroductionCourse overviewDatabase systems conceptsRelational database modelStructured query language (SQL)


Database System ConceptData

Known facts

DatabaseA collection of related data

Database Management System (DBMS)A software system to facilitate the defining, constructing, manipulating, and sharing of a computerized database

Database SystemThe DBMS software together with the data itselfSometimes, the applications are also included


Typical DBMS Functionality

Define a databaseConstruct and load the databaseManipulating the database

Querying, generating reports, insertions, deletions and modifications

Concurrent processing and sharingProtection or securityPresentation and visualization


Database System Environment

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Example of a Database

Webster University Distributed Database Design

Figure 1.2 A database that stores student and course information.

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Example of a Database


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Database ManipulationDatabase manipulation involves querying and updating

P. 9Examples of queriesExamples of updates



Database Approach Characteristics

Self-describing nature of a database systemMeta-data

Insulation between programs and data, data abstraction

Program-data independence

Support of multiple views of the dataVirtual data

Sharing of data and multi-user transaction processing

Concurrency control


Database UsersActors on the scene

Database administrators (DBA)Authorizing access to the databaseAcquiring software, and hardware resourcesControlling and monitoring efficiency of operations

Database designersDefine content, structure, constraints, and functions or transactionsCommunicate with the end-users

End-usersQueries, reportsUpdate the database content

Actors behind the scene


Database Users


Advantages of Database Approach

Controlling redundancyRestricting unauthorized accessProviding persistent storageProviding storage structures for efficient query processingProviding backup and recoveryProviding multiple interfacesRepresenting complex relationships among dataEnforcing integrity constraintsDrawing inferences and actions


Historical Development

Early database applicationsHierarchical modelNetwork model

Relational model based systemsObject-oriented applications: OODBs and ORDBMSsWeb and e-commerce applicationsDatabase for new applications


Data ModelsData model

Data abstractionA collection of concepts that can be used to describe the structure of a databaseEntities, attributes, relationshipsData types, constraints

Categories of data modelsConceptual (high-level, semantic) data modelsImplementation (representational) data modelsPhysical (low-level, internal) data models


Schemas and InstancesDatabase schema

Description of a database

Schema diagramDiagrammatic display of a database schema

Database stateActual data in the database at a particular moment in timeCurrent set of occurrences or instances


Schema Diagram


Three-Schema Architecture


Data IndependenceLogical data independence

The capacity to change the conceptual schema without having to change the external schemas and their application programs

Physical data independenceThe capacity to change the internal schema without having to change the conceptual schema


DBMS LanguagesStructured query language (SQL)Data definition language (DDL)

To specify database conceptual schema

Data manipulation language (DML)To specify database retrievals and updates

DBMS InterfacesStand-alone query language interfacesProgrammer interfaces for embedding DML in programming languages


Database System UtilitiesTo perform certain functions such as:

Loading data stored in files into a databaseData conversion toolsBacking up the database periodicallyReorganizing database file structuresReport generation utilitiesPerformance monitoring utilitiesSorting, user monitoring, data compressionData dictionary


Client-Server Architectures Centralized architectureClient-server architecture

ClientProvide appropriate interfaces and a client-version of the system to access and utilize the server resources

ServerProvides services to clientsDatabase server provides database query and transaction services to clients


Three Tier Client-Server Architecture


Classification of DBMSBased on data model

RelationalNetworkHierarchicalObject-orientedObject-relational

Other classificationsSingle-user vs. multi-userCentralized vs. distributed


Relational Model ConceptsThe relational model is based on the concept of a relationA relation is a mathematical concept based on the ideas of setsRelation: A table of values

Contains a set of rows and columns


Example of a Relation


DefinitionsThe schema, or description of a relation

R (A1, A2, .....An)

CUSTOMER (Cust-id, Cust-name, Address, Phone#)

A tuple is an ordered set of valuesEach value is derived from an appropriate domain

A domain is a set of atomic valuesData type or format

An attribute designates the role played by the domain


DefinitionsThe relation is formed over a subset of the Cartesian product of the setsEach set has values from a domainThat domain is used in a specific role which is the attribute nameGiven R(A1, A2, .........., An)

r(R) dom (A1) X dom (A2) X ....X dom(An)

R: schema of the relationr of R: a specific "value" or population of R


ExampleLet R(A1, A2)

Let dom(A1) = {0,1}Let dom(A2) = {a,b,c}

Then, for example:r(R) = {<0,a> , <0,b> , <1,c> }is one possible “state” or “population” or “extension” r of the relation R, defined over domains D1 and D2It has three tuples


Definition ComparisonInformal Terms Formal Terms

Table Relation

Column Attribute

Row Tuple

Values in a column Domain

Table Definition Schema of a Relation

Populated Table State of the Relation


Characteristics of Relations

Ordering of tuples in a relation r(R)The tuples are not considered to be ordered

Ordering of values within each tupleThe attributes in R(A1, A2, ..., An) and the values in t=<v1, v2, ..., vn> are ordered

Values in a tupleAll values are considered atomic (indivisible)A special null value is used to represent values that are unknown or inapplicable to certain tuples


Relational Integrity Constraints

Constraints are conditions that must hold on all valid relation instancesTypes of constraints

Domain constraintsKey constraintsEntity integrity constraintsReferential integrity constraints


Key ConstraintsUniqueness

A set of attributes of R such that no two tuples in any valid relation instance r(R) will have the same value

MinimalRemoval of any attribute results in a set of attributes that is not a key

If a relation has several candidate keys, one is chosen to be the primary key

The primary key value is used to uniquely identify each tuple in a relation

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Foreign KeyA set of attributes in one relation that references the primary key in another relation

Same domain(s)Value of foreign key either occurs as a value of primary key or is null



Entity and Referential Integrity

Entity integrity constraint

No primary key value can be null

Referential integrity constraint

Foreign key value can be either an existing primary key value or a null value


Update OperationsUpdate operations

Insert a tuple (p. 76)Delete a tuple (p. 77)Update a tuple (p. 78)

Maintain integrity constraintsChild insert restrictChild update restrictParent update restrictParent delete restrict


Relational Database Schema



Exercise 3.16Consider the following relations for a database that keeps track of student enrollment in courses and the books adopted for each course:

STUDENT(SSN, Name, Major, Bdate)

COURSE(Course#, Cname, Dept)

ENROLL(SSN, Course#, Quarter, Grade)

BOOK_ADOPTION(Course#, Quarter, Book_ISBN)

TEXT(Book_ISBN, Book_Title, Publisher, Author)

Specify the foreign keys for this schema, stating any assumptions you make.


SQLStructured query language (SQL)

SQL-86 or SQL1SQL-92 or SQL2SQL-99 or SQL3

Comprehensive database languageData definition (DDL)Data manipulation (DML)

QueryUpdate


Data Definition Language (DDL)

Used to CREATE, DROP, and ALTER the descriptions of the tables (relations) of a databaseData types

NumericCharacter stringBooleanData/time


CREATE TABLESpecifies its name, its attributes and their data typesA constraint NOT NULL may be specified

CREATE TABLE DEPARTMENT ( DNAME VARCHAR(10) NOT NULL,

DNUMBER INTEGER NOT NULL,MGRSSN CHAR(9),MGRSTARTDATE CHAR(9));


CREATE TABLEUse the CREATE TABLE command for specifying

Primary key attributesSecondary keys, andReferential integrity constraints (foreign keys)

CREATE TABLE DEPT( DNAME VARCHAR(10) NOT NULL,

DNUMBER INTEGER NOT NULL,MGRSSN CHAR(9),MGRSTARTDATE CHAR(9),PRIMARY KEY (DNUMBER),UNIQUE (DNAME),FOREIGN KEY (MGRSSN) REFERENCES EMP );


DROP TABLE and ALTER TABLE

Remove a relation (base table) and its definition

DROP TABLE DEPENDENT;

Add an attribute to one of the base relations

ALTER TABLE EMPLOYEE ADD JOB VARCHAR(12);


Retrieval Queries in SQLOne basic statement for retrieving information from a database

SELECT statement

Basic form is a SELECT-FROM-WHERE blockSELECT <attribute list>

FROM <table list>

WHERE <condition>


Simple SQL QueriesQuery 0:

Retrieve the birthdate and address of the employee whose name is 'John B. Smith'

SELECT BDATE, ADDRESS

FROM EMPLOYEE

WHERE FNAME='John'

AND MINIT='B'

AND LNAME='Smith';



Retrieve the name and address of all employees who work for the 'Research' department

SELECT FNAME, LNAME, ADDRESSFROM EMPLOYEE, DEPARTMENTWHERE DNAME='Research'

AND DNUMBER=DNO;

DNAME='Research' is a selection conditionDNUMBER=DNO is a join condition



For every project located in 'Stafford', list the project number, the controlling department number, and the department manager's last name, address, and birthdate

SELECT PNUMBER, DNUM, LNAME, ADDRESS, BDATE FROM PROJECT, DEPARTMENT, EMPLOYEEWHERE DNUM=DNUMBER AND MGRSSN=SSN

AND PLOCATION='Stafford';

There are two join conditionsDNUM=DNUMBER relates a project to its controlling departmentMGRSSN=SSN relates the controlling department to the employee who manages that department


AliasesA query that refers to the same name must qualify the attribute name with the relation nameSome queries need to refer to the same relation twiceQuery 8:

For each employee, retrieve the employee's name, and the name of his or her immediate supervisor

SELECT E.FNAME, E.LNAME, S.FNAME, S.LNAMEFROM EMPLOYEE E, EMPLOYEE SWHERE E.SUPERSSN=S.SSN;


Unspecified Where-ClauseQuery 9:

Retrieve the SSN values for all employees

SELECT SSNFROM EMPLOYEE;

Query 10:Retrieve the SSN and department name values for all employees

SELECT SSN, DNAMEFROM EMPLOYEE, DEPARTMENT;

Resulting CARTESIAN PRODUCT


Use of Asterisk *Q1C:

SELECT *FROM EMPLOYEEWHERE DNO=5;

Q1D:

SELECT *FROM EMPLOYEE, DEPARTMENTWHERE DNAME='Research' AND

DNO=DNUMBER;

To retrieve all the attribute values


Use Of DistinctTo eliminate duplicate tuples in a query result, the keyword DISTINCT is used

Q11:SELECT SALARYFROM EMPLOYEE;

Q11A:SELECT DISTINCT SALARYFROM EMPLOYEE;


Set OperationsUNION, MINUS and INTERSECT operationsQuery 4:

Make a list of all project numbers for projects that involve an employee whose last name is 'Smith' as a worker or as a manager of the department that controls the project(SELECT PNAME

FROM PROJECT, DEPARTMENT, EMPLOYEEWHERE DNUM=DNUMBER AND MGRSSN=SSN

AND LNAME='Smith')UNION

(SELECT PNAMEFROM PROJECT, WORKS_ON, EMPLOYEEWHERE PNUMBER=PNO AND ESSN=SSN

AND LNAME='Smith');


Substring Matching

Query 12:Retrieve all employees whose address is in Houston, Texas

SELECT FNAME, LNAME

FROM EMPLOYEE

WHERE ADDRESS LIKE '%Houston, TX’;


Arithmetic Operations

Query 13:Show the resulting salaries if every employee on the ‘ProductX’ project is given a 10 percent raise

SELECT FNAME, LNAME, 1.1*SALARY AS INCREASED_SAL

FROM EMPLOYEE, WORKS_ON, PROJECT

WHERE SSN=ESSN AND PNO=PNUMBER AND PNAME=‘ProductX’;


Ordering of Query Results

Query 15:Retrieve a list of employees and the projects they are working on, ordered by department and, within each department, ordered alphabetically by last name, first name

SELECT DNAME, LNAME, FNAME, PNAME

FROM DEPARTMENT, EMPLOYEE, WORKS_ON, PROJECT

WHERE DNUMBER=DNO AND SSN=ESSN AND PNO=PNUMBER

ORDER BY DNAME, LNAME, FNAME;


Specifying Updates in SQLThere are three SQL commands to modify the database

INSERTDELETE, andUPDATE


INSERTU1:INSERT INTO EMPLOYEE

VALUES ('Richard', 'K', 'Marini', '653298653', ‘1962-12-30', '98 Oak Forest,Katy,TX', 'M', 37000, '987654321', 4);

U1A:INSERT INTO EMPLOYEE (FNAME, LNAME, SSN)

VALUES ('Richard', 'Marini', '653298653');


DELETEU4:

DELETE FROM EMPLOYEE WHERE LNAME='Brown';

DELETE FROM EMPLOYEE WHERE SSN='123456789';

DELETE FROM EMPLOYEE WHERE DNO=5;

DELETE FROM EMPLOYEE;


UPDATEU5:

Change the location and controlling department number of project number 10 to 'Bellaire' and 5, respectively

UPDATE PROJECTSET PLOCATION = 'Bellaire', DNUM = 5WHERE PNUMBER=10;

U6:Give all employees in the 'Research' department a 10% raise in salary

UPDATE EMPLOYEESET SALARY = SALARY * 1.1WHERE DNO IN = 5;


Reading and HomeworkReadings

Chapter 1, 2, 3, and 4

Week one homework

Documents

Distributed Database Design