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1. Your name here The lecture notes are based on using Microsoft Access interactively as part of the lecture

2. Manipulating Database Content with Relational Algebra and Microsoft Access • How to manipulate information in relational databases • Using relational algebra and Microsoft Access • How to define simple one-table queries • Projection queries • Selection queries • How to define queries that combine multiple tables • Product queries • Join queries • Queries with multiple joins • How to combine relational operations to create complex queries • Defining complex queries with Microsoft Access • How to define queries with set operators • Union, intersection, difference • How to create user interfaces in Access • A video rental checkout form

3. Manipulating Information in Relational Databases • A relational database table • Consists of a set of rows (also called records) • each row in a table has the same number and types of attributes. • When you send a query to the database, it • Finds the appropriate rows of information in the stored tables • Performs the requested operations on the data • Represents the results in a new temporary table • Delivers the results table to the user • Destroys the table when the user no longer needs it

4. Queries and Query Languages • Queries can be represented in many ways • Relational algebra (explained in Chapter 8) • Query by example diagrams (as in Microsoft Access) • SQL, the standard query language (explained in Chapter 9) • 4 basic types of queries • A projection operation produces a result table with • Only some of the columns of its input table. • A selection operation produces a result table with • All of the columns of the input table • Only those rows of its input table that satisfy some criteria. • A join or product operation produces a result table by • Combining the columns of two input tables. • A set operation produces a result table by • Combining rows from one or the other of its input tables • This chapter focuses on manipulating relational tables with relational algebra and Microsoft Access

5. Projection Queries • A projection query selects some of the columns of the input table • project Customer onto (firstName, lastName) • Relational algebra form • firstName,lastName(Customer) • Notice that the result table has fewer rows • Duplicate rows have been removed

6. Projection in Access Query wizard dialog Source table Select button (right arrow) Selected fields

7. Selection Queries • A selection query selects rows that match a selection criteria • select from Customer where lastName = ‘Doe.’ • Relational algebra form • lastName=‘Doe’(Customer)

8. Selection query in Access All fields selected Show button unselected Selection criteria lastName = “Doe”

9. More complex criteria • The selection criterion can be any expression • select from TimeCard where ssn = ‘376-77-0099’ and date < ‘01-mar-2002’ • Shaded rows are result rows • Relational algebra form • ssn=’376-77-0099’ and date<’01-mar-2002’(TimeCard)

10. Complex criteria in Access Selection criterion date<01-mar-2002 Field selection list

11. Product Queries • A product query produces a result table from 2 inputs • Combines the attributes from two different tables • Produces a new table with more attributes than either of the original ones • is product of Employee and TimeCard • Relational algebra form • Employee  TimeCard • Combines every row of one table with every row of other table • We really want to combine an employee and a timecard for a single employee Rows from first time card Rows from second time card

12. Join queries • A join query is a product with a restriction on the result rows • The join condition determines which rows match • Only matching rows are in the result table • Typical join condition is equality of attributes • join Employee and TimeCard where Employee.ssn = TimeCard.ssn • Relational algebra form • Employee⋈Employee.ssn=TimeCard.ssnTimeCard • Some rows of result shown in this table

13. Join query in Access Join line

14. Queries with Multiple Joins • This query has 2 joins • Join Rental and Video • Join that table with Movie • Relational algebra form • accountId, videoId, dateRented, dateDue, title, cost ((Rental ⋈videoId Video) ⋈movieId Movie)

15. Combining Relational Operations • Combine selection, projection, and join in one query • project videoId, title, and dateDue from Rental join Video on videoId join Movie on movieId where accountId=113 and • Relational algebra form • videoId, title, dateDue((accountId=113(Rental) ⋈videoId Video) ⋈movieId Movie)

16. Defining Complex Queries with Microsoft Access Four source tables and three joins Selecting by dateRented Projecting 4 fields

17. Applying Set Operators to Tables • Set operations include • Union, intersection, and difference • Set operations can be applied to any tables with the same shape • The same order and type of attributes • Attribute names do not have to agree • For example • Rental (accountId number, videoId number, dateRented date, dateDue date, cost currency) • PreviousRental (accountId number, videoId number, dateRented date, dateReturned date, cost currency) • Agree in order and type, but not in name • Rental.dateRented vs. PreviousRental.dateReturned

18. Simple User Interfaces in Access Customer information Videos rented by Jane Block Customer navigation buttons

19. A Video Rental Checkout Form • See Access database for details of forms design