Additional Database Notes

8/3/2019 Additional Database Notes

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Database Basics

Objectives of Database Its advantagesand application in Corporate Share ability: An ability to share data resources is a

fundamental objective of database management.This means different people and different processes canthe same actual data at the same time.

Serving differently types of users with varying skill levels

Handling different user views of the same stored data

Combining interrelated dataControlling concurrent updates so as to maintain dataintegrity's



Database Basics

Evolvability Evolvability refers to the ability of the DBMS tochange in response to growing user needs andadvancing technology.

Evolvability is the system characteristic thatenhances future availability of the data resources.

Evolvability is not the same as expandability orextensibility, which imply extending or adding to thesystem, which then grows ever larger.

Evolvability covers expansion or contraction, bothof which may occur as the system changes to fit theever changing needs and desires of the usingenvironment.



Database Basics

Integrity The importance and pervasiveness of the need to

maintain database integrity is rooted in the reality

that man is perfect. Destruction, errors andimproper disclosure must be anticipated and explicitmechanisms provided for handling them. The threeprimary facets of database integrity are:

protecting the existence of the database

Maintaining the quality of the database

Ensuring the privacy of the database



DBMSData Dictionary & Metadata A database contains information about entities of

interest to users in an organization When created, the database itself becomes an

³entity´ about which information must be kept for

various data administration purposes Data dictionary (or system catalog) is a database

about the database Contents of a DD are commonly referred to as

metadata

DD can be updated, queried much as a ³regular´database

DBMS often maintains the DD



DBMS

Benefits of Data DictionaryBenefits include -

improved documentation and control

consistency in data use

easier data analysis

reduced data redundancy

simpler programming

the enforcement of standards

better means of estimating the effect of change.



DBMS

Metadata

Metadata: data that describes the properties andMetadata: data that describes the properties and

context of user data.context of user data.

± ±

but separate from that data;but separate from that data; ± ± Stored as part of the database.Stored as part of the database.

---including data types, field sizes, allowable values,and data context



DBMS



Data Independence

With knowledge about the three-schemes architecture the termdata independence can be explained as followed: Each higher

level of the data architecture is immune to changes of the next

lower level of the architecture.

Physical Independence: Therefore, the logical scheme may stay

unchanged even though the storage space or type of some data

is changed for reasons of optimisation or reorganisation.

Logical Independence: Also the external scheme may stay

unchanged for most changes of the logical scheme. This is

especially desirable as in this case the application software doesnot need to be modified or newly translated.



Distributed DatabaseT ypes of Distributed Database System

Distributed database system are of the following types

Homogenous Distributed Database Systems

Heterogeneous Distributed Database System



Distributed Database H omogenous Distributed Database System

All sites have identical software

T hey are aware of each other and agree to cooperate in processing user requests

It appears to user as a single system



An Homogenous Distributed Database

Systems example

A distributed system connects three databases: hq, mfg, and sales

An application can simultaneously access or modify the data in several

databases in a single distributed environment.



Distributed Database H eterogeneous Distributed Database System

In a heterogeneous distributed database system, at least one

of the databases uses different schemas and software.

A database system having different schema may cause a

major problem for query processing.

A database system having different software may cause amajor problem for transaction processing.



Distributed Database F eatures of Distributed Database System

R eplication

± System maintains multiple copies of data, stored in different

sites, for faster retrieval and fault tolerance. Fragmentation

± R elation is partitioned into several fragments stored indistinct sites

R eplication and fragmentation can be combined

R elation is partitioned into several fragments: systemmaintains several identical replicas of each such fragment.



Distributed Database Advantages Distributed Database System

Availability: failure of site containing relation r does not

result in unavailability of r is replicas exist.

Parallelism: queries on r may be processed by several nodes

in parallel.

R educed data transfer: relation r is available locally at eachsite containing a replica of r.



Distributed Database Disadvantages Distributed Database System

Increased cost of updates: each replica of relation r must beupdated.

Increased complexity of concurrency control: concurrent

updates to distinct replicas may lead to inconsistent data

unless special concurrency control mechanisms are

implemented.

One solution: choose one copy as primary copy and

apply concurrency control operations on primary copy.



Data Warehousing & Data Mining

Benefits of Data Mining Data mining in customer relationship management applications can

contribute significantly to the bottom line.

R ather than randomly contacting a prospect or customer through a call center

or sending mail, a company can concentrate its efforts on prospects that are

predicted to have a high likelihood of responding to an offer. More sophisticated methods may be used to optimize resources across

campaigns so that one may predict to which channel and to which offer an

individual is most likely to respond²across all potential offers.

Businesses employing data mining may see a return on investment

Data mining can also be helpful to human-resources departments inidentifying the characteristics of their most successful employees.



Why choose MS-Access over SPSS /

Excel?

Although there is always overlap, the following rules might help

when deciding when / when not to use MS Access:

MS Access is best used for long-term data storage and/or data sharing.

MS Excel is best used for minor data collection, manipulation,

and especially visualization.

SPSS is best used for minor data collection and especially data

analysis.

It is easy to export data from MS Access to Excel SPSS



What is in an MS-Access file - 1? Although the term ³database´ typically refers to a collection of

related data tables, an Access database includes more than just

data. In addition to tables, you can add:

Saved queries (stored procedures) - organizing and/or manipulating data

F orms ± gui interaction with data, event programming

Reports ± customized results for printing (~ static forms)

Macros and V B programs for extending functionality

Microsoft provides some logical integration of these tools through

³wizards´. H owever, these are pretty basic - most developers

must pick and choose the best approach when implementing

applications.



What is in an MS-Access file - 2?

U nless advanced

techniques are employed,

all entities are stored in

one *.mdb file. Whenrunning, a locking file

(*.ldb) is also visible.

Only the mdb file needs

to be copied to transfer

the database to another computer or location.

Ex.

MSCI_ B yrneGuestLect

ure.mdb



What is in an MS-Access file - 3?

Demographics Ethnicity Labs H & P

Tables

Queries

Forms (Active)Reports (Static)

VB + Macros ± Event Driven Automation, etc.



Microsoft Access Module 1

Summary

MS- Access is a powerful relational database program. It

has many integrated features and can be greatlycustomized to fit most personal/departmental needs for

data collection and storage.




Creating / Working with T ables



Tables Glucose Measurement

Database

We wish to construct a database to track waking glucosemeasurements for an indefinite amount of time on 100

patients receiving 3 possible drug combinations.

Why would this be difficult in MS-Excel or SPSS?



Tables Overview

j T hink of Access as a collection of spreadsheets that are

relationally linked .

S T O R E D A T A O N E T I M E / O N E

P L A C E

D O

N O T S T O R

E C A L C U L A T E D

D A T A

Demographics

Patient_IDFname

Lname

Address

Phone

Gender

RaceDOB

Height

Glucose

Glucose_IDPatient_ID

Date

Weight

Med_ID

Glucose

Meds

Med_IDDrugCombonation



Table Demonstration - Live

General Setup for T ables

Describe General Options Show Validation Rule

Relationships

Lookup Option



Table Relationships - Live

Table Relationships

Describe Cascade Features



Table Import / Link - Live

Importing a T able

makes a copy of

existing data

Linking a T able lets

you control existing

data through Access

(Exercise Caution !)

N ote that you

may import

non- Access

files.



MS Access Module 2 Summary Data storage principles

1. Attempt to store data 1 time / 1 place;2. Do not store data that may be calculated from other

fields (utilize queries); and 3. Strive for very discrete data storage (no ambiguity ±

garbage in / garbage out).

4. Choose real or arbitrary (autonumber) uniqueidentifier for each record.

RelationshipsU se table relationships to automatically cascade delete

and update records.

Other Data Sources

Import = Copy; Link = Live Connect.




Creating / Working with Queries



One Table Q uery Example - Live

Right-Click + Add to addtable(s)

Drag and Drop Fields

Custom sort

by one or

more fields.

U se this

button to

toggle

between

design, sheet

and SQL

views.



2-Table Q uery Example - Live

Drag and Drop Fields

Right-Click + Add to add table(s)

Note that relationship often automatic.

Calculated Field

BMI: [Weight]/([Height]/100)^2

Right-Clicking gray area above

field enables property changes.



Q uery Calculating Fields

N ame the calculated field, then type a colon, then

type the equation using brackets ( [ ] ) around

table fields. If there is ambiguity in the field

names between tables, you may need to type

table.[field] format.

Ex: B MI: [Weight]/([ H eight]/100)^2



Q uery Sorting Data

Choose Ascending or Descending in the Sort Row

This query would sort by Gender THEN by Race.



Q uery Filtering Data

This query will return all records in the database for:Females

who are not white

whose height are greater than 150 cm

and who weigh between 60 and 70 kg

Y o

u n e e d n o t ³ s h o w ´ t h e d a t a f i e l d t

o u s e a s a f i l t e r .



Q uery Filter Operators

= equals

> greater than

>= greater than or equal

< less than

<= less than or equal

<> not equal to

Betweenbetween two values

Is Null field is empty

is not null field is not empty

Like Matches a pattern (Like John*)

OR Logical OR (one or other is true)

AND Logical AND (both are true)

etc.



Q uery Grouping Data - 1

Clicking the Totals Button Enables

Grouping, Counting and Statistical

Options

Notice new ³Total´ row.

Each field (column) can be set.

Running this

Query indicates

there are 203

Females and 261Males in the

database.



Q uery Grouping Data -2

Totals Options Include:

Group By

Sum

Avg

Min

Max

Count

StDev

Var



Q uery Export Data

Create and Save

Query1)

Use OfficeLinks (Excel Toggle Option) to

³Analyze it with Excel´2)

Data Automatically Exported

to Excel3)




Creating / Working with F orms/Reports



Graphical User Interface (GUI)

Although it is possible to enter data directly into a table,

you can enhance data quality by forcing data entry

through forms.

Depending upon your users, you may wish to set things up

so they never even see the database window. In other

words, you can design your application so they only touch

the data through programmed forms.



Graphical User Interface (GUI)

Continuing with the glucose database we formulated

earlier, we¶ll now attempt to build a graphical user

interface to:

Collect Data

Periodically report data through pre-formatted reports

Quit the program



GUI Forms/Report Live

Out of Program

Additional Database Notes

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