Catholic University College of Ghana FiapreSunyani DATABASE SOFTWARE

Catholic University College of Ghana Fiapre-Sunyani DATABASE SOFTWARE DEVELOPMENT INFORMATION TECHNOLOGY II Audrey Asante, Faculty of ICST

DATABASE • Database is an organized collection of integrated files. • Database may be shared or distributed. • Shared database is shared by users in one company or organization in one location. Shared databases can be found in local area networks.

• Distributed database is one that is stored on different computers in different locations connected by a client/server network. An example is the bank • Who is a database administrator? • A person who coordinates all related activities and needs for a corporation’s database.

• What is the responsibility of a database administrator? – System Security – Backup and recovery – Performance monitoring – Database design, implementation and operation – Coordination with users

Database Storage Hierarchy • It consists of the levels of data stored in a computer file: bits, bytes (characters), fields, records, files and databases. • Field is a unit of data consisting of one or more characters. Example is Name, Address, Social Security No • Record is a collection of related fields. Example is the person’s name or address or social security no

• File is a collection of related records. Example is data collected on everyone. • Database is an organized collection of integrated files. Example is a database of a company

Key Field • It is a field that is chosen to uniquely identify a record so that it can be easily retrieved and processed.

File Management System • File-based system: a collection of application programs that perform services for the endusers such as the production of reports. Each program defines and manages its own data.

File Management System • Disadvantages – Data redundancy or duplication – Lack of data integrity – Separation and isolation of data – Incompatible file formats – Data dependence

Database Management System • A software system that enables users to define, create, maintain, and control access to the database.

Database Management System • Advantages – Control of data redundancy – Data consistency – Improved security – Enforcement of standards – Improved data accessibility and responsiveness

Database Management System • Disadvantages – Cost – Security – Privacy – Additional hardware cost – Complexity

TYPES OF DATABASE ORGANIZATION • • Hierarchical Network Relational Object Oriented

Hierarchical Database • In this type of database, fields or records are arranged in related groups resembling a family tree, with lower-level records subordinate to higher-level records. A lower-level record is called a child, and a higher-level record is called a parent. The parent record at the top of the database is called the root record. A parent in a hierarchical database may have more than one child, but a child always has only one parent. This is called a one-to-many relationship. Used principally on mainframes

Network Database • A network database is similar to a hierarchical DBMS. The difference is that each child record in the network database can have more than one parent record. In the network database, a child record is identified as a member whiles a parent is referred to as owner. This is also principally used with mainframes. The network database is more flexible than hierarchical because different relationships may be established between different branches of data.

Relational Database • Relational database relates or connects data in different files through the use of a key field, or common data element. Data elements are stored in different tables made up of rows and columns. All related fields must have a key field that uniquely identifies each row. It is more flexible than hierarchical and network database models.

Object Oriented Database • This type of database handles new data types, including graphics, audio, and video which can be combined with text into a multimedia format. An object oriented database system uses “objects” software written in small, reusable chunks, as elements within database files. An object consists of data in the form of text, sound, video and pictures and instructions on the action to be taken on the data.

Features of DBMS • Data Dictionary: a procedures document or disk file that stores definitions or a description of the structure of data used in the database. It may monitor the data being entered to make sure it conforms to the rules defined during data definition such as field name, field size, type of data.

Features of DBMS • Query Language: is an easy-to-use computer language for making queries to a database and for retrieving selected records. • Utilities: programs that allow one to maintain the database by creating, editing, and deleting data, records and files. • Report Generator: a program users may employ to produce an on-screen pr printed document from all or part of a database.

Features of DBMS • Access Security: a feature allowing database administrators to specify different access privileges for different users of a DBMS • System Recovery: a feature that enables database administrators to recover contents of the database in the event of a hardware or software failure.

Software development • Algorithms are a set of ordered steps for solving a problem. • A program is a list of instructions that the computer must follow in order to process data into information.

• Application software may be packaged or customized. • Packaged software is the kind that one buys from a computer store or mail-order house or download from a vendor’s website, which is the kind used by most PC users • Packaged software is an off-the-shelf prewritten program developed for sale to the general public. • Share and freeware

Customized software • It is a software designed for a particular customer. It is an application program that is created or custom-made. Customized software is written to perform a task that cannot be done with packaged software.

Programming • It is a specialized form of the age old process of problem solving. Problem solving typically involves four steps: – Understanding the problem: defining the problem clearly – Devising a plan for solving the problem: what resources are available? people? information? a computer? Software? Data? How might those resources be put to work to solve the problem? – Carrying out the plan: this phase often overlaps with the previous step, since many problem solving schemes are developed on the fly

Programming process • There are four step process – Defining the problem – Devising, refining, and testing the algorithm – Writing the program – Testing and debugging the program Most programming problems are far too complex to solve all at once. To turn a problem into a program, a programmer typically creates a list of smaller problems.

• Each of these smaller problems can be broken into subproblems that can be subdivided in the same way. This process, called stepwise refinement, is similar to the process of developing an outline before writing a paper or a book. Programmers sometimes refer to this type of design as top-down design because the design process starts at the top, with the main ideas, and works down to the details

• The result of stepwise refinement is an algorithm-a set of step-by-step instructions that, when completed, solves the original problem. Programmers typically write algorithms in a form called pseudocode (a cross between a computer language and plain english). When the details of an algorithm are in place, a programmer can translate it from pseudocode into a computer language.

Control structures • A computer can’t understand this algorithm, but the pseudocode is clear to any person familiar with control structures (logical structures that control the order in which instructions are carried out). • This algorithm uses three basic control structures: sequence, selection, and repetition

• Sequence control structure is a group of instructions followed in order from the first through the last. Eg. – Set answer to a random value between 1 and 100 display “guess a number between 1 and 100” – Set counter to 0 • Repetition control structure is a looping mechanism. It allows a group of steps to be repeated several times, usually until some condition is satisfied.

• A selection (or decision) is used to make logical decisions. That is to choose between alternative courses of action depending on certain conditions. It typically takes the form of “if(some condition is true), then(do something) else (do something else)

Testing the algorithm • Testing the algorithm is the next step but not the same as testing the program. This is testing designed to check the logic of the algorithm. We can test it by following the instructions using different sets of numbers.

Programming languages and methodologies • Low level languages – Machine language – Assembly language: a language that’s functionally equivalent to machine language but is easier for people to read, write, and understand. Programmers use alphabetic codes that correspond to the machine’s numeric instructions. • High level languages: it falls between natural human languages and precise machine languages

• High level programs hides most of the nitty gritty details of the machine operations from the programmer. • High level language allows the programmer to focus on what to do, while assembly language forces the programmer to focus on how to do it. • It allows transportation from one machine to the other • They need to be partially rewritten to adjust to differences among hardware, compilers, operating systems, and user interfaces

• Structured programming: a technique to make the programming process easier and more productive. It breaks the big, complicated machine into more manageable modules, each of which has a clearly defined task. Modular programs are easier to understand debug • A programmer combines the modules using sequence, repetition and selection (basic control structures)

• Object oriented programming: it is a collection of objects. Objects contain both data and instructions and can send and receive messages. OOP makes it easy to use features from one program in other programs, so programmers don’t have to start from scratch with every new program.

Visual programming • It enables programmers to create large portions of their programs by drawing pictures and pointing to on-screen objects, eliminating much of the tedious coding of traditional programming. It saves hours of coding time, especially when creating user interfaces

Languages for users • Some computer languages are designed with nonprogrammers in mind – Macro languages (scripting languages) are built into many applications, utilities and operating systems eg. Macro in access, spreadsheet to build a program, vba in office – Fourth generation languages

Fourth Generation Languages • 4 GLs use English-like phrases and sentences to issue instructions • They are nonprocedural, not like pascal, c and basic which are procedural languages. • Non procedural languages enable users to focus on what needs to be done, not on how to do it. • It also increases productivity because programmers can often get results by typing a few lines of code rather than a few pages.

Programming for the web

PROGRAMMING • It is also called software engineering. It is a multistep process for creating that list of instructions. • There are five steps: – Clarify the problem – Design a solution – Code the program – Test the program – Document and maintain the program

Clarify the programming needs • • • Clarify objectives and users Clarify desired outputs Clarify desired inputs Clarify desired processing Feasibility of implementing the program Document the analysis

Feasibility • Technical feasibility: can the required hardware and software be purchased or developed? Is the technology reliable? Does the system provide for accurate, reliable and secure data? • Economic feasibility: cost, good investment • Operational feasibility: needs of the organization, changes in the work procedure, system be developed on a timely schedule • Organizational: support goals and strategy,

Data collection techniques • • • Document review Interview Questionnaire Observation sampling

Modeling tools • Graphic representation of a system – System flowchart – Data flow diagram – Data dictionaries – Decision tables

Design the program • User interface design • Database design • Process design

3. Code the program • A programming language is a set of rules that tells the computer what operations to do.

4. Test the program • Desk checking is simply reading through or checking the program to make sure that its free of errors and that the logic works • Debug the program means to detect, locate and remove al errors in a computer program. The debugging step is sometimes called alpha testing • Run real-world data: it is sometimes alled beta testing

DOCUMENT AND MAINTAIN THE PROGRAM • Prepare user documentaton