Data, Information, and Databases BDIS 6.1 BSAD 141 Dave Novak.

Data, Information, and Databases

BDIS 6.1

BSAD 141

Dave Novak

Topics Covered Information types: transactional –vs-

analytical Five characteristics of information quality Database versus a DBMS RDBMS: advantages and terminology Multi-user issues

The Need for High-Quality Information Data are everywhere

Which data are important?

Which data should the organization store?

Which data need to be further manipulated?

Which data are required to make different types of decisions?

How does the organization convert various data into information that is needed?

The Need for High-Quality Information Recall difference between data and

information from Lecture #1

The Need for High-Quality Information The need to obtain and analyze the many

different levels, formats, and granularities of organizational information to make decisions

The Need for High-Quality Information

CRITICAL TO REMEMBER!Decisions are only as good as the quality

of the data and information that are used to make the decisions…

Crap in Crap out• Using technology to help you make a

decision using poor quality data doesn’t help

Data Quality Problems

Example of Low Quality Data

Characteristics of High Quality Information 1) Accurate 2) Complete 3) Consistent 4) Unique 5) Timely

1) Accurate

Are the data (is the information) correct, precise, and exact?

For example:Are the data factual?Are values error-free?Have data been verified?

• Correct spelling• Precise numbers

2) Complete

Are the data whole (complete) and do they have all the necessary parts?

For exampleAre there missing values or pieces of

data?• Full street address• Area code along with phone number• Empty fields• Full Names

3) Consistent

Are the data are in agreement with themselves and with known facts?

For exampleDoes summary information agree with

detailed information? Can you reconcile the data? • Do mathematical manipulations yield correct

results?• Are data manipulations performed

consistently for the entire data set?

4) Unique Are the data unique (one of a kind) or are

there redundant, repetitious or unnecessary data stored in the same database?For example:

• Are there duplicate records for the same “event”?

• Are there different versions of “the same” file or event (which is the latest or most accurate?)

5) Timely Are the data current with respect to

decision-making needs? Timeliness depends on the situation

Real-time information – Immediate, up-to-date information

Real-time system – Provides real-time information in response to requests

“Real-time” is a relative description that depends on the use or need

How can data be of “poor” quality? Customers intentionally enter

inaccurate information to protect their privacy or because they are irritated

Different data entry standards and formats

Operators enter abbreviated or erroneous information by accident or to save time

Third party and external information contains inconsistencies, inaccuracies, and errors

What is a Database? Database – a collection of information

organized in a way that provides efficient retrieval

There are electronic and physical databases (paper/print)

A database can be a very simple collection of data such as alphabetically arranging names in an address book

What is a Database Management System (DBMS)?

Database management systems (DBMS) – A set of computer programs / software that allow users to store, modify, query, and retrieve data in a systematic and controlled manner

Database Management System (DBMS)

A database (the physical collection of data) is typically not portable across different DBMSLike application software, different DBMS are

generally designed to work with specific system software and specific database schema

A database is typically something inside the DBMS, although in the case of a MS Excel workbook the database is a standalone object

Database Management System (DBMS)

A very popular and common DBMS is the relational DBMS (RDBMS)

A standard program and user interface is the Structure Query Language (SQL)A programming language used to create,

modify, and retrieve information from a database

Different databases use different (proprietary) variations to standard SQL

Database Management System (DBMS)

According to the following source (which I did not verify with the Gartner report) the top five commercial RDBMS vendors in 2011 were:

http://itknowledgeexchange.techtarget.com/eye-on-oracle/oracle-the-clear-leader-in-24-billion-rdbms-market/

Oracle (≈ 50% market share)IBM (≈ 20% market share)Microsoft (≈ 17% market share)SAPTeradata

Database Management System (DBMS)

Oracle: Oracle Database and MySQL IBM: DB2 and Informix Microsoft: SQL Server SAP: Sybase Enterprise and Sybase IQ Teradata

Single File Data Management

MS Excel is a database, but it is not a DBMS! Each worksheet is a single large two-

dimensional matrix A database is simply an organized

collection of data that can be accessed A DBMS is software that is used to

manage the database and provides a set of tools used to manipulate and query data

Relational Database Management System (RDBMS) Data are organized as a set of formal tables Data can be accessed and combined in

different ways without reorganizing the data within the tables• Data can be manipulated in different ways and

combined with data in other tables without altering the original data in the table

RDBMS can be easily extended / scaled – new data and new categories of data can be added without changing existing data

RDBMS Terminology

Data model – A picture of logical data structures that detail the relationships among data elements

Metadata – Formal description of data structures (like tables and fields) and any constraints of the table or values within the table

Data about the containers of data

RDBMS Terminology

Data dictionary – Compiles all of the metadata about the elements in the data model

Entity Sets (Tables) Relational table or entity set –

Each table consists of columns (fields/attributes) and rows (records/entities)

The table has a name that describes the group of related entities within the tableFor example, a table labeled

“Student” would contain a group of student entities

Entity / Record / Row A person, place, thing,

transaction, or event about which data are being collected and storedThe individual rows in a table

contain entitiesEach row is also referred to as

a record Example?

Attributes / Field / Column

The data elements that describe the characteristics of a specific entityThe columns in each table contain the

attributes Example?

What is a Relationship?

1) When designing a relational DB, data need to be separated into tables that contain related data elementsFor example we would not store data

related to customer (name, address, phone, etc.) and data related to the customer’s particular order (orderID, date, shipping method, etc.) in the same table

What is a Relationship?

All information specific to a customer would go into a “Customer” table

All information specific to the specific orders would go into an “Order” table

We would then create a relationship between the tables to match a particular customer with a particular order

What is a Relationship?

A relationship in an RDB is an association between the entities within the different tablesThere are THREE (3) types of

relationships:• One-to-One (1:1)• One-to-Many (1:M)• Many-to-Many (M:M)

Creating Relationships Through Keys KEYS are used to create

relationships between the entities in different tables in the RDBPrimary key

Foreign key

Creating Relationships Through Keys For our purposes:

Every table in a RDB MUST have a primary key

The foreign key is not required in every table and will only appear on the “many” side of the relationship

Advantages of RDBMs RDBMS advantages from a

business perspective include1) Flexibility2) Scalability and performance3) Improved information integrity

(quality)• Reduced information redundancy

4) Information security

1) Flexibility Handle changes quickly and easily Provide users with different views of

the dataArranging data items in different

ways depending on the user needShowing a particular user only some

of the available fields while not showing them other fields

1) Flexibility: Schema

Different database schema can be “owned” by or associated with different users

The schema is a user personalized set of tables, views, and indexes

2) Scalability and Performance A DBMS must expand to meet

increased demand, while maintaining acceptable performance levelsScalability – Refers to how well a

system can adapt to increased demands

Performance – Measures how quickly a system performs a certain process or transaction

3) Information Integrity

Information integrity – a measure of information quality Know that data have not been entered

incorrectly or altered in an unauthorized manner

Integrity constraint – rules that help ensure the quality of informationWe will discuss entity integrity and

referential integrity (there is also domain integrity)

3) Information Integrity: Controlling Redundancy

Redundant data are ok if they serve a specific purpose such as being used as backup directly linked to the sourceBackup systems promote fault tolerance,

Unintentional redundancy is not good Wasted storageDifficult to modifyPossible inconsistencies

4) Information Security

Information is an organizational asset and must be protected

RDBMS offer several security features Access level – Determines the level of

access each individual user has • Who can access the DBMS

Access control – Determines the types of things each group can do• Types of access, such as power to create,

modify, delete, and/or read• Which types of SQL statements can be

executed

Multiuser Issues

DBMS serve many different users with different needs

Many users may require concurrent access to the same data

Must preserve integrity of data and the performance of the system

Multiuser Issues

Problem: if multiple users (say tens or even hundreds of users) access the same data concurrently, how does the DBMS allow one user to change data without being overwritten by another user? This is typically referred to as the Lost-update problem

Multiuser Issues

Concurrent transactions are addressed through the use of transactions and locksTransactions – single indivisible action

that affects some data Once a transaction is committed, it is

permanent and changes are visible to all users

If transaction is not committed, changes are “rolled back” or reversed

Multiuser IssuesLocks – literally “locks” the data so that

changes cannot be made on the data while another transaction is in process

Enterprise DBMS

Learning Outcomes

Five characteristics of quality information Define database, DBMS, RDBMS, and

supporting components and terminology Advantages of RDBMS What is SQL? Describe the lost-update problem and how it

is addressed