(c) 2000, the university of michigan 1 database application design handout #5 february 4, 2000

(C) 2000, The University of Michigan

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Database Application Design

Handout #5

February 4, 2000


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Course information

• Instructor: Dragomir R. Radev ([email protected])

• Office: 305A, West Hall

• Phone: (734) 615-5225

• Office hours: Thursdays 3-4 and Fridays 1-2

• Course page: http://www.si.umich.edu/~radev/654w00

• Class meets on Fridays, 2:30 - 5:30 PM, 311 WH


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Foundations of relational implementation

(cont’d)


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Expressing queries in relational algebra

Type Format Example

Set operations +, -, intersection,union, product

STUDENT [Name] – JUNIOR [Name]

Selection Relation WHEREcondition

CLASS WHERE Name = ‘A’

Projection Relation [list ofattributes]

STUDENT [Name, Major, Age]

Join (Inner join) Relation1 JOIN(condition) Relation2

STUDENT JOIN (SID =StudentNumber) ENROLLMENT

Outer join Relation1 LEFTOUTER JOIN(condition) Relation2

STUDENT LEFT OUTER JOIN (SID= StudentNumber) ENROLLMENT


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Examples

SID Name Major GradeLevel Age

100 JONES HISTORY GR 21

150 PARKS ACCOUNTING SO 19

200 BAKER MATH GR 50

250 GLASS HISTORY SN 50

300 BAKER ACCOUNTING SN 41

350 RUSSELL MATH JR 20

400 RYE ACCOUNTING FR 18

450 JONES HISTORY SN 24

STUDENT


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Examples (Cont’d)

StudentNumber ClassName PositionNumber

100 BD445 1

150 BA200 1

200 BD445 2

200 CS250 1

300 CS150 1

400 BA200 2

400 BF410 1

400 CS250 2

450 BA200 3

ENROLLMENT


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Examples (Cont’d)

Name Time Room

BA200 M-F9 SC110

BD445 MWF3 SC213

BF410 MWF8 SC213

CS150 MWF3 EA304

CS250 NWF12 EB210

CLASS


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Examples (Cont’d)

Full set of relations:JUNIOR (Snum, Name, Major)

HONOR-STUDENT (Number, Name, Interest)

STUDENT (SID, Name, Major, GradeLevel, Age)

CLASS (Name, Time, Room)

ENROLLMENT (StudentNumber, ClassName, PositionNumber)

FACULTY (FID, Name, Department)


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Examples (Cont’d)• What are the names of all students?

• What are the student numbers of all students enrolled in a class?

• What are the student numbers of all students not enrolled in a class?

• What are the numbers of students enrolled in the class ‘BD445’?

• What are the names of the students enrolled in class ‘BD445’?

• What are the names and meeting times of ‘PARKS’ classes?

• Wwhat are the grade levels and meeting rooms of all students, including students not enrolled in a class?


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Structured Query Language (SQL)


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SQL Overview

• ANSI Standard

• Multitude of implementations

• SQL92 (ANSI)

• Not a programming language!

• Two major modes of use: embedded and interactive


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Projections in SQL

SELECT SID, Name, MajorFROM STUDENT

SELECT MajorFROM STUDENT

SELECT DISTINCT MajorFROM STUDENT


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Selections in SQL

SELECT SID, Name, Major, GradeLevel, AgeFROM STUDENTWHERE Major =‘MATH’

SELECT *FROM STUDENTWHERE Major =‘MATH’

SELECT *FROM STUDENTWHERE Major =‘MATH’ AND Age > 21


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Selections in SQL (Cont’d)

• Set values for the condition (IN, NOT IN)

• Ranges (BETWEEN)

• LIKE

• Wild cards (%, _)

• IS NULL


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Sorting in SQL

• ORDER BY

• ASC, DESC


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Built-in functions

• COUNT, SUM, AVG, MAX, MIN

• SELECT COUNT(*)FROM STUDENT

• SELECT COUNT(Major)FROM STUDENT


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Grouping

• GROUP BY

• HAVING

• Example:SELECT Major, COUNT(*)

FROM STUDENTGROUP BY MajorHAVING COUNT(*) > 2

• Ordering (WHERE is computed first)


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Subqueries

SELECT NameFROM STUDENTWHERE SID IN

(SELECT StudentNumber FROM ENROLLMENT WHERE ClassName = ‘BD445’)


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Joins in SQL

• Using more than one table in a SELECT

• Comparing subqueries and joins– not equivalent

• Outer joins (ANSI vs. Access)


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EXISTS and NOT EXISTS

SELECT DISTINCT StudentNumberFROM ENROLLMENT AWHERE EXISTS

(SELECT * FROM ENROLLMENT B WHERE A.StudentNumber =

B.StudentNumber AND A.ClassName NOT = B.ClassName)


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EXISTS and NOT EXISTS (Cont’d)

SELECT Student.NameFROM STUDENTWHERE NOT EXISTS

(SELECT * FROM ENROLLMENT WHERE NOT EXISTS

(SELECT * FROM CLASS WHERE CLASS.Name = ENROLLMENT.ClassName AND ENROLLMENT.StudentNumber =

STUDENT.SID))


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Inserting dataINSERT INTO ENROLLMENT

VALUES (400,’BD445’,44)

INSERT INTO ENROLLMENT(StudentNumber,ClassName)VALUES (400,’BD445)

INSERT INTO JUNIORVALUES(SELECT SID, Name, MajorFROM STUDENTWHERE GradeLevel = ‘JR’)


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Deleting data

DELETE STUDENTWHERE STUDENT.SID = 100

DELETE ENROLLMENTWHERE ENROLLMENT.StudentNumber IN

(SELECT STUDENT.SID FROM STUDENT WHERE STUDENT.Major = ‘Accounting’)

DELETE STUDENTWHERE Student.Major = ‘Accounting’

Ordering!


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Updating data

UPDATE ENROLLMENTSET PositionNumber = 44WHERE SID = 400

UPDATE ENROLLMENTSET PositionNumber = MAX (PositionNumber) + 1WHERE SID = 400


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Database design using E-R Models


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E-R Design

• Transforming user requirements represented using E-R models into relational database designs


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Readings for next time

• Kroenke– Chapter 10: Database application design

• YRK (optional)– Chapter 8: Database application architectures

– Chapter 9: CGI programming

(c) 2000, the university of michigan 1 database application design handout #5 february 4, 2000

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