IFF 1414 Intro to Database. Notes

Transcription

1 1 IFF 1414 Intro to Database Notes

2 Definition of database Database Management Systems Database Model DBMS Categories MS Access Relational database Data Hierarchy MS Access objects 2

3 3 Database is an organized collection of related information (e.g. Student Registration, Inventory and Sales, Flight Reservation) Purpose: To integrate individual items of data as an organized collection; can be transformed into useful information Organized- by fields, records and files using specific model; for easy access and manipulation Collection- not one but group of data

4 A database 4 A structure that can store info about multiple types of entities, attribute of those entities and relationship between entities Entity person, place, object, idea or event. In relational database, each entity has its own table. Row represents unique data for one entity Attributes characteristics or property of an entity; field or column in a table

5 5 Is a database program is a software system that uses a standard method of storing, retrieving, and running queries on data. provides ways for the data to be modified or extracted by users or other programs. Examples : Microsoft Access, Lotus Approach, Corel Paradox, dbase, MySQL, SQL Server, Oracle, FileMaker and FoxPro

6 6 Reduced data redundancy same information is available to different users, increase the chances of data integrity e.g same data fields are not repeated in different files, lower the expense of storage Improved data integrity data is accurate, consistent and up to date

7 Advantages of databases and DBMS software 7 More program independence the program and file formats are the same, one or several programmers can spend less time maintaining files Increased user productivity Increased security

8 Disdvantages of DBMS 8 Cost issues - installing and maintaining a database is expensive, particularly in a large organization. There are costs associated with training people to use it correctly Security issues possible for unauthorized users to get pass the safeguards, destroyed by fire, earthquake, theft or hardware/software problems. Regularly make backup copies and store elsewhere Privacy issues may hold info that should not be used for unintended purposes, intruding people s privacy, eg: medical data used inappropriately for job promotion.

9 DBMS Models (arrangements) describe how data are organized and the methodology for storing and retrieving data 9 Hierarchical Network Relational Object-Oriented

10 Hierarchical model fields or records are arranged in related groups resembling a family tree (upside-down tree) 10 A lower-level record is called a child. A higher-level record is called a parent. The parent record at the top of the database is called the root record. Each entry has one parent node. One parent can have many children but one child (node) can have only one parent.

11 Hierarchical DBMSs are the oldest, used on mainframes 11 Still used in some types of passenger reservation systems Accessing or updating data is very fast because the relationships have been predefined.

12 Limitations of Hierarchical DBMS: 12 The structure must be defined in advance, it is quite rigid. There may be only one parent per child and no relationships among the child records. Adding new fields to database records requires the entire database to be redefined.

13 Departure Kuala Lumpur 13 Arrival Penang Kota Kinabalu Johor Bahru Kuantan Flight Number Passenger Izzati Ismil Ahmad Azfar Azhar Puteri Farhana Abu Zaid Masuri Hierarchical A Nationwide Airline Reservation System

14 Relational model data elements are stored in different tables Each table is made up of records (rows, also known as tuples) and fields (columns, also known as attributes). - A table is called a relation. - Keys are used to match up records in different tables. A key is a collection of one or more fields in one table whose values (data) match corresponding fields in other tables. - The keys help to define the relationships between tables.

15 Relational model more flexible than hierarchical and network database models. Advantages: User does not have to be aware of any structure can be used with little training Entries can be easily added, deleted or modified Popular for microcomputer DBMS such as Access and Paradox. Limitation: Some searches can be time consuming. 15

16 Staff Table field 16 Common key Post and Dept Table record Relational

17 17 Network model similar to hierarchical except that each child record (node) can have more than one parent record. Used principally with mainframes, network database is more flexible than hierarchical - different relationships may be established between different branches of data. Limitations: still requires the structure be defined in advance and there are limits to the number of links that can be made among records.

18 Network Model Student Course Registration 18 Course Accounting Statistics Economics Teacher Nor Hazni Nik Haslina Norlida Siti Hajar Student Syazwan Asyraf Siti Hanis Megat Tariq Asma Amatullah

19 Object-Oriented model suitable for unstructured data such as photos, graphics, audio and video. Also known as object database - Important in businesses related to technological convergence and storage of data in multimedia form 19

20 OODBMS uses objects, software written in small, reusable chunks, as element within database files. An object consists of : Data in the form of text, sound, video, and pictures Instructions on the actions to be taken on the data 20

21 Most current implementations are actually object-relational database Products that can be used to manage objectrelational data: MS Access widely used on personal computers MS SQL server used to share data on Microsoft NT networks Oracle popular Web-commerce database DB2 IBM mini and mainframe data storage software

22 2 basic DBMS categories 22 Personal DBMS for single-user environment; can be networked and shared but no more than 10 concurrent users Client-Server DBMS support multiple users in network environment; used powerful server; store a large amount of data; client PCs request data from server, then do query, update and report on it; use front-end (e.g. Access runs on PC) and back-end (runs on server) *** Differences between the 2 categories amount of data can be stored, number of concurrent users supported, network capabilities and level of data security

23 Find information Add, delete, and modify records Sort records Analyze data Generate reports 23

24 24 Database file: a collection of related tables Table: a collection of records that identify a category of data, such as Customers, Orders, or Inventory. Information is stored in form of rows (records) and columns (fields) Record : a row of information in a table - one complete set of fields of an entity Field : a column in a table; a single attribute of an entity (a person, place, object, event, or idea) Data/field value: actual data of an attribute of an entity

25 25 - multiple tables can be linked to produce combined output from all tables. How does Relational Database work? Tables can be a master table or transaction table A master table contains a primary key A transaction table contains a common field A common field links two tables to each other, thus ensuring connection between the data in the tables within the same database.

26 26 A field that uniquely identify each record. Must be unique. Prevents duplicate record from being entered to the table. Is used to control the order of records. It makes it faster for the database to locate records in the table. Is used to create link between tables in the database. Foreign Key used to match the values in one table to those in another table

27 Plan: recognize the objective. Create: create table to hold data by defining the table structure. Enter and Edit: Enter data and correct errors. Preview and Print : Print the hardcopy. 27

28 28 Navigation Pane Objects Tab a collection of data about specific field Access Objects Printed output from queries or tables View To automate repetitive database tasks Button Access Work Area

29 30 Is a collection of data about specific field Examples: Student table Course table Registration table Form Create a data-entry form to enter data into a table Unlike table entry, form entry is more user friendly

30 To view, change and analyze data in different ways. Can be used as the source of records for form and reports. Types of query: Select query Action query (Update, Delete, Make-Table, Append) Crosstab query Parameter query 31

31 An effective way to present your data in a printed format Since you have control over the size and the appearance of everything in the report, you can display the information the way you want to see it. 32

32 If the user normally opens the same form after opening a database, the task can be simplified by automatically opening the form when the database is launched Provide the simplest way to automate recurring tasks 33

33 Title bar displays the title of the product, Microsoft Access. Close button at the right side. Menu bar Contain a list of menu names. Database window toolbar contains button that allows you to perform certain task more quickly the menu bar. 34

34 Taskbar- at the bottom of the screen the start button, any active windows, and the current time. Status bar - contains special information about the task on which you are working Database window is a special window that allows you to access easily and rapidly a variety of objects. 35

35 36 Create a database file by assigning a filename. Create and save a table 1. the structure of the table must be designed to determine the data type and the property of each field. 2. Assign a name to the table, then click OK button to save. Adding records to a table. 1. Data are entered through the datasheet view. Any changes or editing can be done here. 2. As soon as you have entered a record and moved to another record, the original record is saved

36 37 The structure of a table contains : Fieldname each field in a table must have a unique name, can be up to 64 characters, can contain letter, digits, spaces and some punctuation symbol. Cannot contain period (.), exclamation mark (!), square bracket ([]) and accent grave (`). Not start with a space. Data type indicates the type of data the field will contain Description Access allows you to enter a detailed description of the field.

37 Design View of Client Table 38

38 Use backspace to delete the fieldname Use delete key to delete the field an extra field Use insert key to add a field in between existing fields Use primary key button to change the primary key field. To start over, click close button and click No. 39

39 40 Text Memo Numbers Date/Time Currency AutoNumber Yes/No OLE object Hyperlink Lookup wizard

40 1. Text - Text entries (alphabet, number or both) up to 255 characters. Can contain any characters. 2. Memo - A maximum characters can be entered in a Memo Field. 3. Numbers - Digits only used for calculation 4. Date/Time Any valid date in mm/dd/yy 5. Currency - Like Number field, but formatted to display decimal places and currency symbol 41

41 42 6. AutoNumber - A unique sequential number that is automatically incremented by one whenever a new record is added to a table 7. Yes/No - Accepts only Yes/No, True/False, or On/Off 8. OLE object e.g picture created in other program, can be linked to or embedded 9. Hyperlink field that stores hyperlinks or URLs 10. Lookup wizard allows to choose a list of values from another table using a combo box

42 43 Field size Format Input Mask Caption Default Value Validation Rules Validation Text Required Allow zero length Indexed

43 1. Field size -Sets the maximum length of characters in the field 2. Format -Specifies how data displays in a table and prints 3. Input mask - Specifies data entry by controlling what data is required and displayed in a field 44

44 45 4. Caption - Specifies a field label other then the fieldname. 5. Default Value - Automatically fills in certain value for this field in new records as you add to the table 6. Validation Rules - Limits data entered in a field to values that meets certain requirements.

45 7. Validation Text - Specifies the message to be displayed when the associated Validation Rule is not satisfied. 8. Required - Specifies whether or not a value must be entered in a field. 9. Allow zero length - Whether or not a value must be entered in a field. 10. Indexed- Set a field as index 46

46 Field Size 47 Text: 1 to 255, default is 50 characters long Number**: Byte, Integer, Long Integer, Single or Double Yes/No and Date/Time : Not Available

47 Format: the way data displays and prints 48 Text: > for uppercase or < for lowercase Number: Fixed - to fix the decimal place Currency - with currency sign and decimal places fixed Scientific - for very small or large numbers Percentage multiplied by 100 with % symbol Date: Formatted to short date (default American date), medium date and long date

48 Format: the way data displays and prints 49 Date can be formatted to: Short date (default date) - follows American date with the setting mm/dd/yyyy e.g: 4/25/2009 Medium date with the setting dd-mmm-yy e.g: 25-Apr-09 Long date with the day, month, day in full spelling and the year e.g: Saturday, April 25, 2009

49 50 Byte - stores whole numbers from 0 255; size -- 1 byte of disk space Integer - stores numbers from -32,768 to 32,767 (no fractions); size 2 bytes Long integer - from -2,147,483,684 to 2,147,483,687 (no fractions); size 4 bytes Single - from 1.401E-45 to E38 for positive values; size 4 bytes Double from 4.94E-324 to 1.798E308; size 8 bytes Decimal from -10^28-1 to 10^28-1; size 12 bytes

50 Input Mask pattern for entering data 51 2 types of characters: Literal and Mask Appear as it is Represents the data to be entered Matric Number Eg: M M is Literal Pattern for Matric Number Eg: M000000;;@ placeholder 0s are Mask (6 required digits) nothing between semicolons, only typed char are saved.

51 0 required digit 9 optional digit # - optional digit, space, +, - L required letter? optional letter A required letter or digit a optional letter or digit & - required character or space C optional character or space \ - to have mask treated as literal 52

52 53 Expression or value automatically entered for new records Eg: In field Program in Student table. ENGIN is assigned for all records Default value = 0, is default for any number field.

53 54 Limits the expressions/values that can be entered in a field. Eg: To allow only certain program: Econs or Laws or IRK To limit the entry of allowance: >=500 and <=1000 To limit entry of date purchased: >#12/31/2004# If records already exist before the rule is imposed, make sure all data fulfill the rule; after the rule is imposed, any invalid entry is not accepted. Validation Text - The message that you want to appear whenever the validation rule is violated.