Your name hereThe lecture notes are based on using Microsoft Access

interactively as part of the lecture

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

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

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

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

firstName lastName

Anita Morehouse

Jane Block

Carroll Breaux

Cherry Hamilton

Catherine Harrison

Jane Doe

Joseph Greaves

accountId lastName firstName street city state zipcode balance

101 Block Jane 345 Randolph Circle Apopka FL 30458- $0.00

102 Hamilton Cherry 3230 Dade St. Dade City FL 30555- $3.00

103 Harrison Katherine 103 Landis Hall Bratt FL 30457- $31.00

104 Breaux Carroll 76 Main St. Apopka FL 30458- $35.00

106 Morehouse Anita 9501 Lafayette St. Houma LA 44099- $0.00

111 Doe Jane 123 Main St. Apopka FL 30458- $0.00

201 Greaves Joseph 14325 N. Bankside St. Godfrey IL 43580- $0.00

444 Doe Jane Cawthon Dorm, room 642 Tallahassee FL 32306- $10.55

Projection in Access

Query wizarddialog

Source table Select button(right arrow)

Selected fields

Selection Queries• A selection query selects rows

that match a selection criteria– select from Customer where

lastName = ‘Doe.’ • Relational algebra form

lastName=‘Doe’(Customer)

accountId firstName lastName street city state zipcode balance

111 Jane Doe 123 Main St. Apopka FL 34331 0.00

444 Jane Doe Cawthon Dorm, room 642

Tallahassee FL 32306 10.55

Selection query in Access

Show button unselected

Selection criterialastName = “Doe”

All fields selected

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)

ssn date startTime endTime storeId paid

145-09-0967 01/ 14/ 2002 8:15 12:00 3 yes

245-11-4554 01/ 14/ 2002 8:15 12:00 3 yes

376-77-0099 02/ 23/ 2002 14:00 22:00 5 yes

376-77-0099 03/ 21/ 2002 14:00 22:00 5 yes

145-09-0967 01/ 16/ 2002 8:15 12:00 3 yes

376-77-0099 01/ 03/ 2002 10:00 14:00 5 yes

376-77-0099 01/ 03/ 2002 15:00 19:00 5 yes

Complex criteria in Access

Field selection list

Selection criteriondate<01-mar-2002

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

Employee.ssn lastName firstName TimeCard.ssn date startTime endTime storeId paid

145-09-0967 Uno Jane 145-09-0967 1/ 14/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

245-11-4554 Toulouse Jie 145-09-0967 1/ 14/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

376-77-0099 Threat Ayisha 145-09-0967 1/ 14/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

479-98-0098 Fortune Julian 145-09-0967 1/ 14/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

579-98-8778 Fivozinsky Bruce 145-09-0967 1/ 14/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

145-09-0967 Uno Jane 145-09-0967 1/ 16/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

245-11-4554 Toulouse Jie 145-09-0967 1/ 16/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

376-77-0099 Threat Ayisha 145-09-0967 1/ 16/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

479-98-0098 Fortune Julian 145-09-0967 1/ 16/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

579-98-8778 Fivozinsky Bruce 145-09-0967 1/ 16/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

145-09-0967 Uno Jane 245-11-4554 1/ 14/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

245-11-4554 Toulouse Jie 245-11-4554 1/ 14/ 2002 8:15:00 AM 12:00:00 PM 3 Yes

Rows from second time card

Rows from first time card

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.ssn TimeCard

• Some rows of result shown in this table

Employee. ssn

last Name

first Name

TimeCard. ssn date start Time

storeId paid end Time

145-09-0967 Uno Jane 145-09-0967 01/ 14/ 2002 8:15 3 no 12:00

145-09-0967 Uno Jane 145-09-0967 01/ 16/ 2002 8:15 3 no 12:00

245-11-4554 Toulouse Jie 245-11-4554 01/ 14/ 2002 8:15 3 no 12:00

376-77-0099 Threat Ayisha 376-77-0099 02/ 23/ 2002 14:00 5 no 22:00

Join query in Access

Join line

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)

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)

Defining Complex Queries with Microsoft Access

Four source tables and three joins

Selecting by dateRented

Projecting 4 fields

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

Simple User Interfaces in Access

Customer navigation buttons

Videos rented by Jane Block

Customer information

A Video Rental Checkout Form

• See Access database for details of forms design