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CS101 - Introduction to Computing - Lecture Handout 37

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Database Software

Focus of the last Lecture was on Data Management

  • First of a two-lecture sequence
  • We became familiar with the issues and problems related to data-intensive computing
  • We also found out about flat-file and tabular storage

Data Management

  • Keeping track of a few dozen data items is straight forward
  • However, dealing with situations that involve significant number of data items, requires more attention to the data handling process
  • Dealing with millions - even billions - of inter-related data items requires even more careful thought

Issues in Data Management

Data Entry

  • New titles are added every day
  • New customers are being added every day
  • That new data needs to be added accurately Data Updates
  • All those actions require updates to existing data
  • Those changes need to be entered accurately

Data Security

  • All the data that BholiBooks has in its computer systems is quite critical to its operation
  • The security of the customers’ personal data is of utmost importance. Hackers are always looking for that type of data, especially for credit card numbers
  • This problem can be managed by using appropriate security mechanisms that provide access to authorized persons/computers only
  • Security can also be improved through:
    • Encryption
    • Private or virtual-private networks
    • Firewalls
    • Intrusion detectors
    • Virus detectors

Data Integrity

  • Integrity refers to maintaining the correctness and consistency of the data
    • Correctness: Free from errors
    • Consistency: No conflict among related data items
  • Integrity can be compromised in many ways:
    • Typing errors
    • Transmission errors
    • Hardware malfunctions
    • Program bugs
    • Viruses
    • Fire, flood, etc.

Ensuring Data Integrity

  • Type Integrity
  • Limit Integrity
  • Referential Integrity
  • Physical Integrity

Data Accessibility

  • What is required is that:
    • Data be stored in an organized manner
    • Additional info about the data be stored so that the data access times are minimized
  • A solution to this concurrency control problem: Lock access to data while someone is using it

DBMS

  • A DBMS takes care of the storage, retrieval, and management of large data sets on a database
  • It provides SW tools needed to organize & manipulate that data in a flexible manner
  • It includes facilities for:
    • Adding, deleting, and modifying data
    • Making queries about the stored data
    • Producing reports summarizing the required contents

Database

  • A collection of data organized in such a fashion that the computer can quickly search for a desired data item

OS Independence

It provides an OS-independent view of the data to the user, making data manipulation and management much more convenient

What can be stored in a database?

  • As long as it is digital data, it can be stored:
    • Numbers, Booleans, text
    • Sounds
    • Images
    • Video

In the very, very old days …

  • Even large amounts of data was stored in text files, known as flat-file databases
  • All related info was stored in a single long, tab- or comma-delimited text file
  • Each group of info – called a record - in that file was separated by a special character;
    vertical bar ‘|’ was a popular option
  • Each record consisted of a group of fields, each field containing some distinct data item

The Trouble with Flat-File Databases

  • The text file format makes it hard to search for specific info or to create reports that include only certain fields from each record
  • Reason: One has to search sequentially through the entire file to gather desired info, such as ‘all books by a certain author’
  • However, for small sets of data – say, consisting of several tens of kB – they can provide reasonable performance

Tabular Storage: Features & Possibilities

  1. Similar items of data form a column
  2. Fields placed in a particular row – same as a flat-file record – are strongly interrelated
  3. One can sort the table w.r.t. any column
  4. That makes searching – e.g., for all the books written by a certain author – straight forward
  5. Similarly, searching for the 10 cheapest/most expensive books can be easily accomplished through a sort
  6. Effort required for adding a new field to all the records of a flat-file is much greater than adding a new column to the table

CONCLUSION: Tabular storage is better than flat-file storage
We will continue on with tables’ theme today

Today’s Lecture:

Database SW

  • In our 4th & final lecture on productivity software, we will continue our discussion from last week on data management
  • We will find out about relational databases
  • We will also implement a simple relational database

Let’s continue on with the tabular approach. We stored data in a table last time, and liked it. Let’s revisit that table and then put together another one

Table from the Last Lecture

Title Author Publisher Pric InStoc
Good Bye Mr. Bhola Altaf Khan BholiBooks 100 0 Y
The Terrible Twins Bhola Champion BholiBooks 199 Y
Calculus & Analytical Geometry Smith Sahib Good Publishers 325 N
Accounting Secrets Zamin Geoffry Sung-e- Kilometer Publishers 29 Y

Another table …

Customer Title Shipment Type
Aadil Ali Good Bye Mr. Bhola 2002.12.26 Air
Aadil Ali The Terrible Twins 2002.12.26 Air
Miftah Muslim Calculus & Analytical Geometry 2002.12.25 Surface
Karen Kaur Good Bye Mr. Bhola 2002.12.24 Air

This & the previous table are related

  • They share a column, & are related through it
  • A program can match info from a field in one table with info in a corresponding field of another table to generate a 3rd table that combines requested data from both tables
  • That is, a program can use matching values in 2 tables to relate info in one to info in the other

Q: Who is BholiBooks’ best customer?

  • That is, who has spent the most money on the online bookstore?
  • To answer that question, one can process the inventory and the shipment tables to generate a third table listing the customer names and the prices of the books that they have ordered

The generated table

Customer Price
Aadil Ali 1000
Aadil Ali 199
Miftah Muslim 325
Karen Kaur 1000

Can you now process this table to find the answer to our question

Relational Databases

  • Databases consisting of two or more related tables are called relational databases
  • A typical relational database may have anywhere from 10 to over a thousand tables
  • Each column of those tables can contain only a single type of data (contrast this with spreadsheet columns!)
  • Table rows are called records; row elements are called fields
  • A relational database stores all its data inside tables, and nowhere else
  • All operations on data are done on those tables or those that are generated by table operations
  • Tables, tables, and nothing but tables!

RDBMS

  • Relational DBMS software
  • Contains facilities for creating, populating, modifying, and querying relational databases
  • Examples:
    • Access
    • FileMaker Pro
    • SQL Server
    • Oracle
    • DB2
    • Objectivity/DB
    • MySQL
    • Postgres

The Trouble with Relational DBs

  • Much of current SW development is done using the object-oriented methodology
  • When we want to store the object-oriented data into an RDBMS, it needs to be translated into a form suitable for RDBMS

The Trouble with Relational DBs

  • Then when we need to read the data back from the RDBMS, the data needs to be translated back into an object-oriented form before use
  • These two processing delays, the associated processing, and time spent in writing and maintaining the translation code are the key disadvantages of the current RDBMSes

Solution?

  • Don’t have time to discuss that, but try searching the Web on the following terms:
  • Object-oriented databases
    • Object-relational databases

Classification of DBMS w.r.t. Size

  • Personal/Desktop/Single-user (MB-GB)
    • Examples: Tech. papers’ list; Methai shop inventory
    • Typical DMBS: Access
  • Server-based/Multi-user/Enterprise (GB-TB)
    • Examples: HBL; Amazon.com
    • Typical DMBS: Oracle, DB2
  • Seriously-huge databases (TB-PB-XB)
    • Examples: 2002 – BaBar experiment at Stanford (500TB); 2005 – LHC database at CERN (1XB)
    • Typical DMBS: Objectivity/DB

Some Terminology

  • Primary Key is a field that uniquely identifies each record stored in a table
  • Queries are used to view, change, and analyze data. They can be used to:
    • Combine data from different tables, efficiently
    • Extract the exact data that is desired
  • Forms can be used for entering, editing, or viewing data, one record at a time
  • Reports are an effective, user-friendly way of presenting data. All DBMSes provide tools for producing custom reports.
  • Data normalization is the process of efficiently organizing data in a database. There are two goals of the normalization process:
    • Eliminate redundant data
    • Storing only related data in a table

Before we do a demo, let me just mention my favorite database application:

Data Mining

  • The process of analyzing large databases to identify patterns
  • Example: Mining the sales records from a BholiBooks could identify interesting shopping patterns like “53% of customers who bought book A also bought book B”.
    This pattern can be put to good use!
  • Dat a mining often utilizes intelligent systems’ techniques

Let’s now demonstrate the use of a desktop RDBMS

  • We will create a new relational database
  • It will consist of two tables
  • We will populate those tables
  • We will generate a report after combining the data from the two tables

Access Tutorial

http://www.microsoft.com/education/DOWNLOADS/tutorials/classroom/office2k/ acc2000.doc

Today’s Lecture:

  • In this final lecture on productivity software, we continued our discussion from last week on data management
  • We found out about relational databases
  • We also implemented a simple relational database

Next Lecture’ Goals

(Cyber Crime)

  • To know the different types of computer crimes that occur over cyber space
  • To familiarize ourselves with with several methods that can be used to minimize the effect of these crimes
  • To get familiar with a few policies and legislation designed to tackle cyber crime