Database Management Systems: A Comprehensive Guide
What is a Kiosk?
A kiosk is a computer terminal featuring specialized hardware and software designed within a public exhibit that provides access to information and applications for communication, commerce, entertainment, and education.
Data Definition Language (DDL)
A data definition language or data description language (DDL) is a standard for commands that define the different structures in a database. DDL statements create, modify, and remove database objects such as tables, indexes, and users. Common DDL statements are CREATE, ALTER, and DROP.
Data Manipulation Language (DML)
A data manipulation language is a language that enables users to access and manipulate data in a database. The goal is to provide efficient human interaction with the system. Data manipulation involves:
- Retrieval of information from the database – SELECT statement
- Insertion of new information into the database – INSERT statement
- Deletion of information in the database – DELETE statement
- Modification of information in the database – UPDATE statement
A query language is a part of DML involving information retrieval only. The terms DML and query language are often used synonymously. A popular data manipulation language is Structured Query Language (SQL). This is used to retrieve and manipulate data in a relational database. Other forms of DML are those used by IMS/DLI, CODASYL databases, such as IDMS and others. Data manipulation language comprises the SQL data change statements, which modify stored data but not the schema or database objects.
There are two types of DML:
- Procedural: The user specifies what data is needed and how to get it.
- Nonprocedural: The user only specifies what data is needed. This is easier for the user but may not generate code as efficient as that produced by procedural languages.
Database Management System (DBMS)
A database management system is a software package with computer programs that controls the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications. A database is an integrated collection of data records, files, and other objects. A DBMS allows different user application programs to concurrently access the same database.
Database Servers
Database servers are dedicated computers that hold the actual databases and run only the DBMS and related software. Typically databases available on the database servers are accessed through command line or graphic user interface tools referred to as Frontends; database servers are referred to as Back-ends. Such type of data access is referred to as a client-server model.
The Relational Model
The relational model for database management is a database model based on first-order predicate logic, first formulated and proposed in 1969 by Edgar F. Codd. In the relational model of a database, all data is represented in terms of tuples, grouped into relations. A database organized in terms of the relational model is a relational database. The purpose of the relational model is to provide a declarative method for specifying data and queries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for answering queries.
Database Concepts: Items, Fields, Records, Values, and Tables
You may have people’s names, people’s addresses, people’s phone numbers, and maybe even people’s birthdays. There is a common element here – people. In this example, each person is considered an “item”. So, an item is what the database is storing information about. When you were recording information in your address book, what did you ask the people? What is your address? What is your phone number? etc. Each question that we ask about our item is a “field”.
Now, say you make new friends and want to add their information to your address book. You will ask questions, get the answers and create a new “record”. So a record is a set of information (made up of fields) stored in your database about one of the items. A “value” is the actual text or numerical amount or date that you put in while adding information to your database. When you put all the information together in a grid (like you do in a spreadsheet), a collection of similar records creates a table.
Key Fields and Record Uniqueness
When creating a database, an important feature is record uniqueness in every table. It is important to be able to distinguish between different items having duplicate values. Uniqueness helps to avoid accidental duplication of records caused by user or computer error. This can be achieved by using some number or value that uniquely identifies a record. If such a unique value does not exist in your fields, as the database designer, you can create a special additional field in a table where unique numbers or values can be assigned for each new entry. Therefore, every table has a key field which ensures that there are 100% unique values throughout the database. Every database table should have one or more fields designated as a key. You can assign a unique value to this key for differentiating records that may have similar names or addresses.
Speaker Notes in Presentations
Speaker notes can be short or long texts that can be used as a reference by the presenter while making a presentation. An area of a PowerPoint or OpenOffice Impress slide that is hidden during the presentation is reserved for notes for the speaker. Here you as the presenter can note important key points that you wish to cover during the presentation.
You can print these notes out, accompanied by a thumbnail version of the appropriate slide, to keep as a handy reference to use when you are making your oral presentation. This can help you to communicate specific points related to each slide and make the presentation effective for the audience.
Presentation Tips
- Do a thorough spell check across all slides.
- Perform a manual spell check for terms that are not included during the standard spell check in the presentation software; NOT all terms (particularly technical terms such as biological names, etc.) will be checked.
- Remove irrelevant content such as images or clip arts, terms, etc. if they are not required.