1DB&SQL 1-

Databases & SQL

Teacher: Henny Klein

email

E.H.Klein@rug.nl

contact:

wednesday 14-16

room 11 - 426

All material and assignments on Nestor

2DB&SQL 1-

Content of the course

• First block

CH 1 t.m. 5

Basic knowledge for the design and manipulation of relational databases

• Second block

CH 6 t.m. 10

other types of databases

processes in a DBMS

distributed systems

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Content of practical sessions

• Access: basic manipulations: tables, relations, QBE, forms, reports

• Access- SQL– data definition– data manipulation– queries

• Programming in Access– functions, event handling (VBA, DAO)

• Building an application

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Your own design!

• You will train with example databases but every student has also to build his/her own database

• during lectures we will discuss your design

• in practical exercises you can build your database, formulate queries, etc.

Assignment for this week (details later):

Think of a theme for your database!

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The book

• Gives the essential information, but concise, so in lectures time is spent on explanation and examples.

• Gives exercises, use them as a method of self assessment

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Grading rules

Design+Project SQL/VBA Exam30% 30% 40%

Design exercises as homework

Individual project

SQL and VBA: practical exercises

Tentamination: mostly theory, some SQL, no VBA

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Card catalogue, textfile, DBMS

• How did people search books in a library before the computer era?

• What are advantages of an electronic system?

• What are advantages of a database system compared to a textfile?

• How did departments of organizations communicate before the computer era?

• What are advantages of a DBMS here?

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Database management systems

Systematic, structured data storage• each data item is stored once, no redundancy• data integrity and security ensured• data available for distinct applications• concurrent use of data• differents views on data

DBMS used in many environments:• administration (products, clients, employees)• information (catalogues)• research (data storage, data mining)• online applications

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Information Science and databases

• DBMS:the standard system to store information, so often important in your work, and even beforehand:

– many students have to handle databases in their ….. in public or private organizations

– in a research …….. or in in your own research project

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The multi-layer system

Presentation of the data(views)

Access: Forms, reports, VBA, SQLOutside Access: (web)applicaties

Logical description of the data(conceptual level)

DBMS

Operating system (host)

Physical storage of data

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Types of database systems

• early types:– Hierarchical database– Netwerk database

• currently most common:– Relational database– Integration of XML

• developing:– Object oriented database

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Database: conceptual model of reality

???Which information items (attributes) may be useful for the entity

• BOOK• TREE

???

The choice of attributes dependson the properties of the entities

but alsoon the context

A database is a model of reality

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Relational db: example of a table

CODE LEV_NAAM ADRES WOONPLAATS004 Hovenier G.H. Zandweg 50 Lisse009 Baumgarten R. Taksstraat 13 Hillegom011 Struik BV Bessenlaan 1 Lisse013 Spitman en Zn. Achtertuin 9 Aalsmeer014 Dezaaier L.J.A. De Gronden 101 Lisse019 Mooiweer FA. Verlengde Zomerstr. 24 Aalsmeer

Each row represents the data of 1 supplierEach row is uniqueData are split up in simple items (comments??)

Tabel Leveranciers (=suppliers)

Scheme: Leveranciers (code, lev_naam, adres, woonplaats)

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The anatomy of a table / relation

Naam Adres Woonplaats

J.Jansen Poolweg 13 Gorkum

P.Putten Kaaplaan 6 Breda

J.Jansen Weerd 18 Breda

record, entiteitrecord, entityrij, tupelrow, tuple

kolomcolumn

attribuutwaardeattribute value

attribuut, veldnaamattribute, field namekolomkopcolumn heading

tabelkop, schema table heading, scheme

gegevensdata, recordset, body

NB An attribute has a data type and a domain

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Identification required

In a relational database, duplication of data must be prevented.Why?? What are the problems??

It is important to choose a sound identification, for current but also for possible future

Think of a appropriate identification for

students (in Progress)books (in the library)members of a hockey club?

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Identification problems

Which problems may occur by using

NAW-data (Naam Adres Woonplaats)ISBNday of birth?

Often, a system-created unique number is used as the primary key (primaire sleutel).It is easy and makes searching faster.But does it really discern your entities?

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Introduction of database design

• In most cases, one table is not enough for structured data storage

• The next slides show basic principles of database design• Later on, in Chapter 4, relational database design is

discussed at length

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Library as a flat table: redundant data

ISBN Title PubName PubPhone Price1-1111-1111-1 C++ Big House 123-456-7890 $29.950-99-999999-9 Emma Big House 123-456-7890 $20.000-91-335678-7 Fairie Queene Big House 123-456-7890 $15.000-91-045678-5 Hamlet Alpha Press 999-999-9999 $20.000-103-45678-9 Iliad Big House 123-456-7890 $25.000-12-345678-6 Jane Eyre Small House 714-000-0000 $49.000-99-777777-7 King Lear Alpha Press 999-999-9999 $49.000-555-55555-9 Macbeth Alpha Press 999-999-9999 $12.000-11-345678-9 Moby Dick Small House 714-000-0000 $49.000-12-333433-3 On Liberty Big House 123-456-7890 $25.000-321-32132-1 Balloon Small House 714-000-0000 $34.000-55-123456-9 Main Street Small House 714-000-0000 $22.950-123-45678-0 Ulysses Alpha Press 999-999-9999 $34.001-22-233700-0 Visual Basic Big House 123-456-7890 $25.00

Authordata

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Preventing redundancy

The table asserts several times that Big House has Phone xxx

Problems with data redundancy:file sizedata integrity (update/insert anomalies)

Solution:The phone number is an attribute of the publisher, not of the bookSo publisher is an entity on its ownBut how are book and publisher related??

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Relationship Publisher-Book: 1 to many

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Establishing a relationship

ISBN Title Price PubID0-321-32132-1 Balloon $34.00 31-1111-1111-1 C++ $29.95 10-99-999999-9 Emma $20.00 10-91-335678-7 Fairie Queene $15.00 10-91-045678-5 Hamlet $20.00 20-103-45678-9 Iliad $25.00 10-12-345678-6 Jane Eyre $49.00 30-99-777777-7 King Lear $49.00 2

BOOKS

PubID PubName PubPhone1 Big House 123-456-78902 Alpha Press 999-999-99993 Small House 714-000-0000

PUBLISHERS Publisher and book are distinct entity classes, they need distinct tables

Primary key / primaire sleutel

referencing key / verwijzende sleutel

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Author: a multivalued attributeprovisional solutions

ISBN Title Author Field1 Field20-321-32132-1 Balloon Sleepy A B0-321-32132-1 Balloon Snoopy A B0-321-32132-1 Balloon Grumpy A B

ISBN Title Author(s) Field1 Field20-321-32132-1 Balloon Sleepy, Snoopy, Grumpy A B

ISBN Title Author1 Author2 Author3 Field10-321-32132-1 Balloon Sleepy Snoopy Grumpy A

a multivalued field? a repeated field? repeating the bookrecord?

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... and the problems

ISBN Title Author(s) Field1 Field20-321-32132-1 Balloon Sleepy, Snoopy, Grumpy A B

Problems: find an author, sort on an author

ISBN Title Author1 Author2 Author3 Field10-321-32132-1 Balloon Sleepy Snoopy Grumpy A

Problems: find an author, sort on an author, number of author fields? empty fields

ISBN Title Author Field1 Field20-321-32132-1 Balloon Sleepy A B0-321-32132-1 Balloon Snoopy A B0-321-32132-1 Balloon Grumpy A B

Problems: redundancy: integrity problems, filesize

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The relational solution for multiple values

Authors are split up in an additional tableEach record connects one AUTHOR to a BOOK

ISBN Title Field1 Field20-321-32132-1 Balloon A B .. .. .. ..

Table BOOKS

ISBN Author0-321-32132-1 Sleepy0-321-32132-1 Snoopy0-321-32132-1 Grumpy0-91-045678-5 Shakespeare0-555-55555-9 Shakespeare.. ..

Table BOOK-AUTHOR

Rule: attributes contain only one simple value

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complex data

An author may have more attributes:

first namefamily namebirthday ….

how can we design a database for books and authors as separate entities?

what about the relationship?

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Relationship BOOK – AUTHOR: many to many

A1

A4

A2

A3

B1

B2

B3

B4

B5

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Library: Books and authorsAuID AuName AuPhone1 Austen 111-111-11112 Melville 222-222-22223 Homer 333-333-33334 Roman 444-444-44445 Shakespeare 555-555-55556 Joyce 666-666-66667 Spencer 777-777-77778 Mill 888-888-88889 Smith 123-222-222210 Jones 123-333-333311 Snoopy 321-321-222212 Grumpy 321-321-000013 Sleepy 321-321-1111

ISBN AuID0-99-999999-9 10-99-777777-7 50-11-345678-9 20-12-345678-6 10-91-335678-7 70-12-333433-3 81-22-233700-0 40-55-123456-9 90-55-123456-9 100-555-55555-9 50-123-45678-0 60-103-45678-9 30-91-045678-5 50-321-32132-1 110-321-32132-1 120-321-32132-1 131-1111-1111-1 4

ISBN Title … 0-321-32132-1 Balloon 0-91-045678-5 Hamlet 0-555-55555-9 Iliad .. ..

2 entities and a link table(tussentabel)

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Database design

Which entities, which attributes? Which primary key?Book: ISBN, Title, PricePublisher: PubID, PubName, PubPhoneAuthor: AuID, AuName, AuPhone

Which relations?A book has 1publisherA publisher publishes 1 or more books : infinite many

A book has 1 or more authorsAn author writes 1 of more books

U B1 -

S B -

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Entity-Relation Diagram (Ch 2)

Author

Book Publisherpublished by/

publishes

written by/writes

1

MethodStart from one record in a table and write the

relationship type at the other table (1 or )

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Homework

1. Read and note your questions about– Rolland: Ch 1, Ch 3.1Challenge: table 1.1 is not the right representation of the data in fig

1.5 and 1.6. Try to correct it!– Additional info: Brookshear 9.1 en 9.2

2. Think of a theme for your own database project (hobby, useful data, ..) and write down– which entities you discern (at least 3)– which attributes they have– what relationships exist among themCopy your notes and bring them next lecture to discuss and to hand

in!

Next week: chapter 2: ER diagrams