Rapid Application Development

Transcription

1 Rapid Application Development Chapter 6: Development Database Application Tools: Microsoft Access Cr: fisher.osu.edu Dr.Orawit Thinnukool College of Arts, Media and Technology, Chiang Mai University

2 Contents Introduction to Database Database Component Purpose of Database System Database Management Systems Database System Hardware Database System Software Planning the design of database Database Application Introduction: What is Access? What are these objects in ACCESS Data Type :Access Relational Database The database design process Logically structuring data

3 Introduction to Database A database is a place to store information. That information could be sales figures, an inventory of computers you own, a list of key customers, timesheet information; the possibilities are endless. By having the database on your site, you can easily share the information with people who need access to it. The best way to think of a database is as a table. The columns in the table are called fields. There are many types of fields you can create: text, numeric, currency, names, dates, to name a few. The rows in the table are called records. The records contain all the database information.

4 Introduction to Database A database is much more powerful than a simple table. With a table, you can only look at the information in the one way that the table is designed. A database allows you to create many views of your information. Each view allows you to: Select the fields displayed in the view. Pick the order in which the fields appear. Set up a filter to control which records appear in the view. Sort the order in which the records appear. Total up fields in the view. View fields from more than one database.

5 Introduction to Database When you create your own database, you determine how the information appears, what the names of the fields are, what the views look like, and who has access to the database. If you already have information that you would like in your database, you can import that information into the database. You can also export information from your database for use in another program, such as Microsoft Excel

6 Database Component 1. Data : In DBMS, databases are defined, constructed and then data is stored, 2. Database Application: program contains statements that request the DBMS to perform operation on database. The operations may include updating, deleting data etc. 3. Database Management System: It is the set of programs used to handle the database and to control and manage the overall computerized database 4. Database Server: database server is a computer program that provides database services to other computer programs or computers, as defined by the client server model. The term may also refer to a computer dedicated to running such a program. 5. Database Administrator : A person who is responsible for managing the overall database management system is called database administrator or simply DBA.

7 Database Management Systems A database management system (DBMS) is an aggregate of data, hardware, software, and users that helps an enterprise manage its operational data The main function of a DBMS is to provide efficient and reliable methods of data retrieval to many users Most DBMSs deal with several users who try simultaneously to access several data items and, frequently, the same data item MySQL (Oracle) IBM DB/2 Microsoft Access SAP DB Sybase Microsoft SQL Server

8 Database System Hardware A categorize computer memory into two classes: internal memory and external memory ; internal memory is permanent, such as ROM We are interested here only in memory that can be changed by programs. This memory is often known as RAM.

9 Database System Software Users interact with database systems through query languages. The query language of a DBMS has two broad tasks: to define the data structures that serve as receptacles for the data of the database, and to allow the speedy retrieval and modification of data. DBMS software usually contains application development tools in addition to query languages. The role of these tools is to facilitate user interface development. They include forms systems, procedural and nonprocedural programming languages that integrate database querying with various user interfaces, etc.

10 Purpose of Database System Nowadays, database applications were built on top of file systems - Data redundancy and inconsistency Multiple file formats, duplication of information in different files - Difficulty in accessing data Need to write a new program to carry out each new task - Data isolation multiple files and formats - Integrity problems Integrity constraints Hard to add new constraints or change existing ones

11 Purpose of Database System - Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out E.g. transfer of funds from one account to another should either complete or not happen at all - Concurrent access by multiple users Concurrent accessed needed for performance Uncontrolled concurrent accesses can lead to inconsistencies - Security problems

12 Database Models A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated. The most popular example of a database model is the relational model, which uses a table-based format. 1. Hierarchical database model 2. Network model 3. Relational mode l** we also uses this model 4. Object model

13 Database Models

14 Planning the design of database When designing your database, you need to consider: What fields should be in the database? This determines what type of information can be stored in the database. What views of the information are needed? This determines how users can see the information and what appears in printed reports or screen. What are the permission levels for the database? Who should have access to this information? Who can add information? Who can edit it?

15 Database Application A database application is a computer program whose primary purpose is entering and retrieving information from a computerized database. Database application comes from the practice of dividing computer software into systems programs, such as the operating system, compilers, the file system, and tools such as the database management system, and application programs, such as a payroll check processor. On a standard PC running Microsoft Windows, ATM, Registration app et al.

16 Database Application -Banking: all transactions -Airlines: reservations, schedules -Universities: registration, grades -Sales: customers, products, purchases -Manufacturing: production, inventory, orders, supply chain -Human resources: employee records, salaries, tax deductions

17 Introduction: What is Access? Microsoft Access is a relational database management system (DBMS). At the most basic level, a DBMS is a program that facilitates the storage and retrieval of structured information on a computer s hard drive. Examples of well-know industrialstrength relational DBMSes include Oracle Microsoft SQL Server IBM DB2 Informix Well-know PC-based ( desktop ) relational DBMSes include Microsoft Access Microsoft FoxPro Borland dbase

18 Introduction: What is Access? Microsoft generally likes to incorporate as many features as possible into its products. For example, the Access package contains the following elements: A relational database system that supports two industry standard query languages: Structured Query Language (SQL) and Query By Example (QBE); A full-featured procedural programming language essentially a subset of Visual Basic, A simplified procedural macro language unique to Access; A rapid application development environment complete with visual form and report development tools;

19 Introduction: What is Access? A sprinkling of objected-oriented extensions; Various wizards and builders to make development easier

20 What are these objects in ACCESS When you create a database, Access offers you Tables, Queries, Forms, Reports, Macros, and Modules. Here's a quick overview of what these are and when to use them. 1. Tables. 2. Queries 3. Forms 4. Reports 5. Macros 6. Modules

21 What are these objects in Access Table : All data is stored in tables. When you create a new table, Access asks you define fields (column headings), giving each a unique name, and telling Access the data type. Use the "Text" type for most data, including numbers that don't need to be added e.g. phone numbers or postal codes 2. Forms: The basic form has an appearance similar to an index card: it shows only one record at a time, with a different field on each line. If you want to control how the records are sorted, define a query first, and then create a form based on the query. If you have defined a one-to-many relationship between two tables, use the "Subform" Wizard to create a form which contains another form. The subform will then display only the records matching the one on the main form.

22 What are these objects in Access Reports: If forms are for input, then reports are for output. Anything you plan to print deserves a report, whether it is a list of names and addresses, a financial summary for a period, or a set of mailing labels. 4. Wizards : Again the Access Wizards walk you through the process of defining reports table form and queries, which are also automatic created. 5. Macros. An Access Macro is a script for doing some job. Macros can also be used to set one field based on the value of another (the "SetValue" action), to validate that certain conditions are met before a record saved (the "CancelEvent" action) etc.

23 Data Type :Access Think of a field's data type as a set of qualities that applies to all the values contained in the field and that determines what kind of data those values can be. There are ten different data types in Access: Attachment Files, such as digital photos. Multiple files can be attached per record. This data type is not available in earlier versions of Access. AutoNumber Numbers that are automatically generated for each record. Currency Monetary values. Date/Time Dates and times. Hyperlink Hyperlinks, such as addresses. Memo Long blocks of text and text that use text formatting. A typical use of a Memo field would be a detailed product description.

24 Data Type :Access Number Numeric values, such as distances. Note that there is a separate data type for currency. OLE Object OLE objects, such as Word documents. Text Short, alphanumeric values, such as a last name or a street address. Yes/No Boolean values. NOTE THAT : Sometimes, the data in a field may appear to be one data type, but is actually another. For example, a field may seem to contain numeric values but may actually contain text values, such as room numbers. You can often use an expression to compare or convert values of different data types.

25 Relational Database A database is a means of storing information in such a way that information can be retrieved from it. In simplest terms, a relational database is one that presents information in tables with rows and columns. A table is referred to as a relation in the sense that it is a collection of objects of the same type (rows). Data in a table can be related according to common keys or concepts, and the ability to retrieve related data from a table is the basis for the term relational database.

26 Relational Database Data in a table can be related according to common keys (Primary Key (PK) or Florien Key (FK) )

27 The database design process 1. Determine the purpose of your database This helps prepare you for the remaining steps. 2. Find and organize the information required Gather all of the types of information you might want to record in the database, such as product name and order number. 3. Divide the information into tables Divide your information items into major entities or subjects, such as Products or Orders. Each subject then becomes a table. 4. Turn information items into columns Decide what information you want to store in each table. Each item becomes a field, and is displayed as a column in the table.

28 The database design process 5. Specify primary keys Choose each table s primary key. The primary key is a column that is used to uniquely identify each row. An example might be Product ID or Order ID. 6. Set up the table relationships Look at each table and decide how the data in one table is related to the data in other tables. Add fields to tables or create new tables to clarify the relationships, as necessary. 7. Refine your design Analyze your design for errors. Create the tables and add a few records of sample data. See if you can get the results you want from your tables. Make adjustments to the design, as needed. 8. Apply the normalization rules Apply the data normalization rules to see if your tables are structured correctly. Make adjustments to the tables, as needed.

29 Logically structuring data Once the relationships and dependencies amongst the various pieces of information have been determined, it is possible to arrange the data into a logical structure which can then be mapped into the storage objects supported by the database management system. In the case of relational databases the storage objects are tables which store data in rows and columns.

30 Reference e3a0-41b5-aee6-d2331f158280?correlationid=224322a9-d5f8-4ac7-bef2-2fdbfc28a3d5&ui=en-us&rs=en-us&ad=us Gehani, N. (2006). The Database Book: Principles and practice using MySQL. 1st ed., Summit, NJ.: Silicon Press Database design basics. (n.d.). Database design basics. Retrieved May 1, 2010, from Teorey, T.; Lightstone, S. and Nadeau, T.(2005) Database Modeling & Design: Logical Design, 4th edition, Morgan Kaufmann Press. ISBN