1. CSC 110 - Intro. to Computing Lecture 10: Databases

2. Announcements Enjoy the long weekend!

3. Bob Jones7Elvis Gates4 Sam Smith12Steve Young12 Tom Jones10Bob Bledsoe7 Jim Mower8Michael Jones4 Bob DeNiro7Jack Woods10 Greg Martin6Josh Jones9 Mike Marino2Bob Martin7 Jim Woods6Fran McLean12 Bob Denver7Clive Deeker4 Xavier Jobs11Matthew Hertz8 Sam Els3Zoe Elton9 Ernie Smith9Kate Bolter10

5. Problems With Humans Humans cannot process large amounts of data  Get overwhelmed, lost, and miss patterns (Other) people may also make mistakes  Patterns and trends are important, however Suggest methods of improving business Identify new possibilities that can be exploited Hints at unknown relationships

6. One Solution: Databases Databases are programs that store and manage information automatically  Typically used when data is frequently added, modified, or searched for  Examples of databases: Prices & orders from amazon.com Student records in a college Phone calls made/received from a phone number Card catalogue in a library

7. Why Databases Are Useful Computers process 1 data item as easily as they process 10 or 10 billion items  Filter data to return only certain elements E.g., Only consider results for people named “Bob”  Evaluate results on a minute-by-minute basis E.g. Have we made our sales goals yet?  Combine data that are somehow related Let the user look for missed relationships

8. Relational Databases Most common databases today Uses relationships to organize data Starts with a table  Each table contains a collection of records Every record uses identical fields, but may have different values Fields must include at least one unique identifier  Database usually contain multiple tables And define how to combine data between tables

9. Commonly Used Database

10. Database Organization Databases contain several different pieces  Physical database – File(s) holding the tables  Database engine – Software enabling programs and users to read, write, and modify database contents  Database schema – Files specifying what type of data each field in a table stores; also specifies what fields enable tables to relate to one another

11. Physical Database Specifies how data are stored  Has little/no relation to anything else about the database  Usually uses many files to store all the data Little relationship between files and the data Physical database is only meant to be accessed by database engine  May not make sense to actual people

12. Database Schema Specifies what the type of data each field stores Used to interpret the file(s) storing each table  Example schema for Movie table: Movie (MovieId: key; Title, Genre: text; Rating: Enum)

13. Database Engine Program which must be used to access database  Interprets database schema to get/store information in physical database  Ensures requests match what is expected by database  Verifies program/user requesting or modifying data is allowed to do so

14. SQL Stands for Structured Query Language  Usually pronounced “sequel” Language used by database engines  Includes commands retrieve, add, remove, and modify records Expects/requires commands to be given in a very specific format

15. SQL Query Format select Name from Student  Returns Name in each record in Student table select Name from Student where StudentId =2009348  Return the Name of any Student with a StudentId of 2009348 select Name from Student order by Name  Returns sorted list of Names from Student

16. SQL Query Format select * from Student  Return all records from Movie table select * from Student where name like ‘John’ order by StudentId  Return all records from the Student table, sorted by their id numbers, whose name includes a word like “John”

17. Database Design Designing good databases is a tricky, complex process  No single solution works for all data  Often the “best” design is a matter of interpretation But, bad designs limits data’s usefulness  May limit what data can be stored  Cannot access information across tables

18. ER Modeling ER stands for Entity-Relationship Common way of designing databases  Ignores “real-world” issues, implementation  Starts at important data to store  Evaluates relationships between the data Builds tables and fields from there One popular tool for ER modeling is ER diagram

19. ER Diagram Start with boxes Each box captures single concept we wish to consider/capture  Box labels are usually singular noun  Should describe important actor in relationship being modeled Problem Use Homework

20. ER Diagram Add ovals around each of the boxes  Represent important attributes of each box Labels should be simple, declarative noun  Include all details we might want to capture  Each oval should define single piece of data Problem Use Homework ProblemId Answer QuestionNumber PctCorrect HomeworkId DateDueAvg Score DateGiven

21. ER Diagram Show relationships between boxes  Draw line whenever we may wish to connect data  Turn boxes that in middle of relationship into diamonds ProblemHomework ProblemId Answer QuestionNumber PctCorrect HomeworkId DateDueAvg Score DateGiven Use

22. ER Diagram Now build database  Boxes and diamonds become tables  Ovals become fields of the table  Links between tables suggest tables should share at least 1 field in common ProblemHomework ProblemId Answer QuestionNumber PctCorrect HomeworkId DateDueAvg Score DateGiven Use

23. For Next Lecture Finish reading Chapter 12 Be prepared to discuss:  Spreadsheets