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DATA TYPES, DATABASES. Gergely ZAJZON Dr. Med. DATABASE. Simply:structured collection of data. DATABASE. Simply:structured collection of data. DATABASE. Simply:structured collection of data Storage: a collection of tables connecting to each other. DATABASE.

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DATA TYPES, DATABASES

Gergely ZAJZON Dr. Med.


DATABASE

  • Simply:structured collection of data


DATABASE

  • Simply:structured collection of data


DATABASE

  • Simply:structured collection of data

  • Storage: a collection of tables connecting to each other


DATABASE

  • In computer science, a database is a structured collection of records or data that is stored in a computer system so that a computer program or person using a query language can consult it to answer queries.

  • The records retrieved in answer to queries are information that can be used to make decisions.


DATA

  • Data is visualised form of some kind of knowledge. Representative property of somebody or something.

  • From IT perspective: data is coded information, stored in a computer as a signal sequence.

  • Has to be stored in a structured and processable form


DATA - examples

  • PATIENT DATA:- name- birth date

    - address

    - „TAJ” – patient code

    Phone book:- name- address- phone number


INFORMATION

  • The Sesame Street character Cookie Monster describes information as "news or facts about something."

  • Measure unit of information:

    bit: value can be 1 or 0 (true / false).

  • Information is the result of processing, gathering, manipulating and organizing data in a way that adds to the knowledge of the receiver..


INFORMATION

Why do we create databases?

  • Storing and searching of data

  • Retrieval of new informations from stored data collections


DATA TYPES

  • Basic property of data fields

  • Defines:

    • a set of values

    • structure of data

    • allowable operations on those values

  • Makes it possible, that in one column of a table only same type of data can be stored.


BASIC DATA TYPES

  • Can not be divided to further separete parts


COUNTABLE DATA TYPE CLASSESS


REAL DATA TYPE CLASSESSNumeric real data types


DATA TYPE

  • Choosing the correct data type:

    • Helps making your database more structured

    • Eg.: a field containing birth dates should be DATE type.

    • Helps validating your data:

    • Eg.: DATE field can not contain a date like 31. february 2008.

    • You can not enter a text into an INTEGER field


Data Types

  • Binary

    • Database specific binary objects

    • Pictures, digital signatures, etc.

  • Boolean

    • True/False values

  • Character

    • Fixed width or variable size

  • Numeric

    • Integer, Real (floating decimal point), Money

  • Temporal

    • Time, Date, Timestamp


SPREADSHEET <-> DATABASE

  • Spreadsheet (EXCEL table): structured.- search- order- filter

  • Software: Eg.: MS-Excel


SPREADSHEET <-> DATABASE

  • „Excel database”: table with special layout:

  • Rows of the table are connected with eachoter, containing the properties of one selected object. Columns: containing the same kind of property for each object. The table has a header in the first row.


SPREADSHEET <-> DATABASE


SPREADSHEET <-> DATABASE

  • Disadvantages of Spreadsheet

  • The same data set can only be modified by one user at the same time

  • Storage of data is not safe enough

  • Structure of data and connections are not defined


SPREADSHEET <-> DATABASE

  • Disadvantages of Spreadsheet

  • Logical limit: can not use multiple tables easiliy, as connections between tables can not be defined


SPREADSHEET <-> DATABASE

INDIRECT PROPERTY => REDUNDANCY, MISTAKES IN DATA INPUT


DATABASE

  • Data collection organized on the basis of a data model.

  • Contains:

    • data

    • Structure of data

    • Connection rule descriptions


DATA MODEL

  • A logical structure, defining the layou of the stored data.

  • Contains no data values.

  • Only properties of data, structure and possible connections


DATA MODEL

CONCEPTUAL DATA MODEL:

  • Analysis of the informations and connections between them.

  • Independent from software tools

    PHYSICAL DATA MODEL:

  • Structured used in the database:definition of tables, data types, connection

  • Software dependent


CONCEPTUAL DATA MODEL

MOZIK

FILMEK

PK

PK

MOZI_ID

FILM_ID

M

N

MOZINEV

FILMCIM

MOZICIM

HOSSZ

MOZITEL

NYELV

MOZIWEB

RENDEZO


PHYSICAL DATA MODEL

MOZI__FILM

FILMEK

MOZIK

PK

MOZIFILM_ID

PK

N

FILM_ID

MOZI_FK

PK

MOZI_ID

N

1

FILMCIM

1

FILM_FK

MOZINEV

HOSSZ

MOZICIM

VETITES

NYELV

MOZITEL

RENDEZO

MOZIWEB


Parts of a database

  • Attributes (fields)

    • An attribute or field is a component of a record that describes something about an item.

  • Records

    • A record is the representation of an individual item.

  • Table

    • A collection of records

  • Database

    • A collection of tables and rules for accessing the tables


Parts of a database

Record

Tables

Attribute/Field

  • Records become “rows”

  • Attributes/fields become “columns”

  • Rules determine the relationship between the tables and tie the data together to form a database


Referential Integrity

  • Rules to preserve relationships

  • Prevents orphan records

    • Cannot add records on many sides

    • Cannot delete from one side

  • Cascade update

  • Cascade delete


NORMAL FORMS

  • The normal forms (abbrev. NF) of relational database theory provide criteria for determining a table's degree of vulnerability to logical inconsistencies and anomalies. The higher the normal form applicable to a table, the less vulnerable it is to such inconsistencies and anomalies. Each table has a "highest normal form" (HNF): by definition, a table always meets the requirements of its HNF and of all normal forms lower than its HNF; also by definition, a table fails to meet the requirements of any normal form higher than its HNF.

  • The normal forms are applicable to individual tables; to say that an entire database is in normal form n is to say that all of its tables are in normal form n.


Normalizing

  • Dependencies between data are identified

  • Redundant data is minimized

  • Reduces chances of data errors

  • Reduces disk space

  • The data model is flexible and easier to maintain


First Normal Form

  • Eliminate repeating columns in each table

  • Create a separate table for each set of related data

  • Identify each set of related data with a primary key

Benefits: Now we can have infinite phone numbers or company addresses for each contact.

Drawback: Now we have to type in everything over and over again. This leads to inconsistency, redundancy and wasting space. Thus, the second normal form…


Second Normal Form

  • Create separate tables for sets of values that apply to multiple records

  • Relate these tables with a “foreign key”.


Third Normal Form

  • Eliminate fields that do not depend on the primary key.

Is this enough? Codd thought so…

What about “many to many”?


Kinds of Relationships

  • “One to One”

    • One row of a table matches exactly to another

      • One person, one id number, one address

  • “One to Many”

    • One row of a table matches many of another

      • One person, many phone numbers

  • “Many to Many”

    • One row may match many of another or many rows match one row of another


BETEGEK

PK

TAJ

NEV

IRSZ

VAROS

CIM

HAZIORVOS

REND IRSZ

REND VAROS

REND_CIM

RENDMH_TEL

BETEGEK

ORVOSOK

PK

PK

TAJ

PECSÉT

M

N

NEV

ORVOS

IRSZ

IRSZ

VAROS

VAROS

CIM

CIM

TEL


DATA MANAGEMENT LANGUAGE

  • SQL = Structured Query Language

  • DDL – Data Definition (CREATE)

  • DML – Data Manipulation (INSERT, UPDATE, DELETE)

  • QL – Query Language (SELECT)


TABLE TYPES

  • Main (core) tables

  • Subtables

  • Linking tables (association table)

  • Dictionary tables (look-up table, value list)


DATABASE SERVER

  • A database server is a computer program that provides database services to other computer programs or computers, as defined by the client-servermodel. The term may also refer to a computer dedicated to running such a program. Database management systems frequently provide database server functionality, and some DBMS's (e.g., MySQL) rely exclusively on the client-server model for database access.

  • Database Master servers are central and main locations of data while Database Slave servers are synchronized backups of the master acting as proxies.


DATABASE SERVER

  • Special DBMS software

  • user interface is not an important aim

  • Allows multi-user change access

  • Controll of user rights

  • Backup of stored data

  • Transaction management


DATABASE SERVERS

  • Oracle

  • MS-SQL

  • My-SQL

  • PostgreSQL


Gergely Zajzon Dr. Med.

E-mail:[email protected]

Web:http://www.gyogyszerugy.hu

Telefon:+36-20-9604294


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