1. Computer Science & Engineering 2111 Lecture 10 Introduction to Database Management Systems 1

2. Database Terms – Data A collection of numbers and text – 273459368 – Information Meaning derived from the data – SSN: 273-45-9368 2

3. What is a database? A large collection of data stored in a well-defined structure – You can think of a database as An electronic filing system A repository for large amounts of information – Example of a paper database Telephone book Examples of computer databases – Ohio State stores student information in a database – Insurance companies store policy holder information in a database – Your employer stores your information in a database 3

4. Database Software How do I create a database? – Purchase the software We will use MS Access 2010, but there are many database software products – Oracle – Sybase – SQL Server How do I access information in the database? – Purchase a Database Management System (DBMS) A DBMS is a collection of programs that enable you to enter, organize, and select data in a database. – We will use MS Access 2010, but there are many database management softwareproducts 4

5. l Tables - a list of data organized into fields and records l Queries - question structures to sort, filter and select specific information l Forms - structures for screen views of data l Reports - structures for written output of data l Program Modules & Macros - program code to perform specific actions Access DBMS “objects”: 5

6. What is a database Form? Structures for screen view and input of information Used to simplify viewing and inputting of information Datasheet View Form View 6

7. Structures for viewing written output of information What is a database Report? 7

8. File Table Primary Key Each Record is made up of 8 Fields Data Type/Field Type Field Properties A field, or combination of fields, which uniquely identifies a record in a database Primary Key 8

9. How is a database Organized? (Hierarchy of Data in a database) Table Each Record is made up of 8 Fields File 16 Records 9

10. Defining Properties for each Field in a Table For a person’s social security number use: What field type? – Text, Number - Short Integer, Number- Long Integer etc. Should it be optional or required? Does the value need to be within certain limits or from a predefined list? Is there a default value? Would an input mask be appropriate 10

11. How should you decide what information goes on which table? If a fact appears in more than one record of a table, then this fact should probably be defined in another table. – Example: Account number Each fact should change in only one place – Example: Address Calculations shouldn’t be part of the database – Example: Current Balance Select a Primary Key where applicable so you can relate your tables – Example: Account number 11

12. The design should be initially created schematically, and then the database should be created using the chosen database software Steps when setting up a Database 12

13. 1. Decide what information you will store in the database Research Papers database First NameCharge Amount Last NameCharge Date AddressPayment Amount CityPayment Type StatePayment Date Zip Code Home Phone This database is a very simplistic one. Most databases you create will be much more complex. 13

14. 2. Create the layout of the database What tables do you need in your database? How will you set them up? – Divide Tables into Inseparable Fields Address as 1 field – 17 Main St. New York, New York 10002 Address as 4 fields Street Address - 17 Main St. City - New York State - New York Zip code – 10002 What will be the field properties of each field? What will be the primary key for each table? A field, or a collection of fields, whose values uniquely identify each record in a table 14

15. Research Papers Database Table Name: Client Field TypeProperties Fields:Client IDText5 Characters longPrimary Key First NameText25 Characters long Last NameText50 Characters long AddressText60 Characters long CityText25 Characters long StateText2 Characters longDefault Value Zip CodeText5 Characters long Home PhoneText10 Characters longInput Mask Table Name: Charges Field TypeProperties Fields:Client IDText5 Characters long Charge AmountCurrencyNone Charge DateDateInput Mast Table Name: Payments Field TypeProperties Fields:Client IDText5 Characters long Payment AmountCurrencyNone Payment TypeText2 Characters long Payment DateDateInput Mask Table Name: PaymentMethod Field TypeProperties Fields:MethodIDText2 Characters long MethodTypeText20 Characters long 15

16. 3. Create a relationship diagram to identify the table, relationships, primary keys and foreign keys We know the information we want to store, but how do we match a customer’s name to their charges and payments? We need a way to relate these two tables to extract useful information. We can relate these two tables by matching the Client ID Foreign key A field that defines the relationship between 2 tables Must be a primary key (unique) in at least one of the tables The field names on each table do not have to match as long as the information is the same. The related fields must be the same data type number, text etc. 16

17. Table Name: Client Primary Key: ClientID Table Name: Charges Primary Key: None Foreign Key: ClientID On Charges table Foreign Key: ClientID On Payments table Table Name: MethodTypes Primary Key: MethodID Foreign Key: PaymentType On Payments table RELATIONSHIP DIAGRAM FOR RESEARCH PAPERS DATABASE 1 1 1 ∞ ∞ ∞ 17 Table Name: Payments Primary Key: None

18. 4. Create the database using the database software Create tables – Fields – Primary keys – Field Types – Field Properties Create Relationships – “ Join” tables – Enforce Referential Data Integrity A set of rules that specifies what records may exist in each table – A record input with a foreign key must always have a matching record in the primary key table in the relationship Cascade Delete Related Records – Removing any entry in a primary key field will automatically remove all entries in foreign key fields of related tables. Cascade Update Related Records – Updating any entry in a primary key field will automatically update all entries in foreign key fields of related tables. 18

19. ENFORCING REFERENTIAL DATA INTEGERITY CASCADE UPDATE & CASCADE DELETE 19

20. Once Relationships are established you can gather information from one or more tables to answer questions Create a list of account numbers and owner names and total transactions What are the total deposits made by accounts starting with 5? What is the total balance of all accounts held by Jane Doe ? These requests are known as Queries 20