Transcript database

DATABASES & DATABASE MANAGEMENT
SYSTEMS (DBMS). MS ACCESS
•What is a database
•Database terms
•DB constructing stages
•DB models
•Relational model
•Normal forms
•DBMS
•DBMS objects
•SQL
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A database is a collection of associated or related
data. For example, the collection of all information
in a doctor’s office can be referred to as a “medical
office database”.
Information stored in computer storage device is
organized in files. For example, a medical office
database may have files on patient data,
pharmaceutical data, employee data, and so on.
Individual data is stored in records within files. For
example, individual items on patient’s record would
include his (her) name, address, and so on.
Information such as name, address, etc. is referred
to as a field or attribute.
So, databases contain files, files contain records,
and records contain fields or attributes.
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Database constructing stages:
conceptual, logical, physical (program-technical)
To create a database for a certain organization one
must first collect those data, then conceptualize
how data might be organized (what are the
relations between data) with a logical model then
realize a database by the mean of software
physically.
Depending on the database logical model we
classify databases as:
Hierarchical
Network
Relational
Mixed (relational-object oriented, hierarchicalrelational, etc.)
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In early 1970 Dr. Edgar F.Codd introduced the
relational model. The relational model is based
on the idea that if you ignore the way data files are
connected and arrange your data into simple twodimensional, unordered tables, then you can
develop an algebra for queries and focus on the
data as data, not as a physical relation of a logical
model.
Note: consequently, in the most resources you
may find data base terms entity set, entity, and
attribute instead of file, record, and field,
respectively, so that to disconnect the idea of
physical file, record and field from the logical
notion of these things.
A collection of two-dimensional tables with records
is referred to as a relational database.
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No Patient’s name
Address
1
Petrov Ivan
125 Abai ave.
2
Rustemova Aina 68 Dostyk
ave
To arrange the tables so that Codd’s
relational algebra would work, Codd
proposed normal forms: first, second,
third normal forms.
There are also normal forms of BCNF
(Boyce-Codd Normal Form), 4-th, 5-th
normal forms.
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Data Base Management Systems (DBMS) store,
process and retrieve huge volumes of data
DBMS help people to organize data in convenient
for storing, processing, accessing, transmitting
data way
Widely spread DBMS systems: MS Access, Oracle
DBMS main objects:
• Table
• Query
• Form
• Report
• Page
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SQL - structured Query Language built in most
DBMS (PL SQL, MS SQL Server-2003, etc.)
SQL consists of:
•Data Definition Language (DDL)
•Data Manipulation Language (DML)
containing operators & functions to store, process,
access, transfer the needed data
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• DDL helps to define data (data field name and
properties) in a new Data Base
Data types available: text, numeric, currency,
date/time, logical, etc.
• DML makes possible to:
create new Data Base;
delete tables, table fields, records;
insert new data;
edit data;
Calculate (process) data;
Arrange data in order (ascending, descending)
Select needed data, etc.
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