S2.DataStructuresandSQL

7/30/2019 S2.DataStructuresandSQL

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S2:DataStructuresandSQL

ShawndraHill

Spring2013

TR1:30-3pmand3-4:30


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APIs

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PhasesintheDMProcess:CRISP-DM

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BusinessUnderstanding

DataUnderstanding

DataPreparaon

Modeling

Evaluaon

Deployment

www.crisp-dm.org


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CRossIndustryStandardProcess-DM

BusinessUnderstanding:Understandingprojectobjecvesanddata

miningproblemidenficaon

DataUnderstanding:Capturing,understand,exploreyourdatafor

qualityissues

DataPrepara2on:Datacleaning,mergedata,deriveaributesetc.

Modeling:Selectthedataminingtechniques,buildthemodel

Evalua2on:Evaluatetheresultsandapprovedmodels

Deployment:Putmodelsintopracce,monitoringandmaintenance

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DataStructures

Adatastructureisaschemefor

organizingdatainthememory

ofacomputer.

Someofthemorecommonly

useddatastructuresinclude

lists,arrays,stacks,queues,

heaps,trees,andgraphs.Binary Tree


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DataStructures

Thewayinwhichthedatais

organizedaffectsthe

performanceofaprogramfor

differenttasks.

Computerprogrammersdecide

whichdatastructurestouse

basedonthenatureofthedataandtheprocessesthatneedto

beperformedonthatdata.Binary Tree


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Example:AQueue

Aqueueisanexampleofcommonlyusedsimpledata

structure.Aqueuehasbeginningandend,calledthefrontand

backofthequeue.

Dataentersthequeueatoneendandleavesattheother.

Becauseofthis,dataexitsthequeueinthesameorderin

whichitentersthequeue,likepeopleinacheckoutlineata

supermarket.


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Example:ABinaryTree

Abinarytreeisanother

commonlyuseddatastructure.

Itisorganizedlikeanupside

downtree.

Eachspotonthetree,calleda

node,holdsanitemofdata

alongwithaleYpointerandarightpointer.

Binary Tree


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Example:ABinaryTree

Thepointersarelinedupso

thatthestructureformsthe

upsidedowntree,witha

singlenodeatthetop,calledtherootnode,andbranches

increasingontheleYand

rightasyougodownthe

tree.Binary Tree


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ChoosingDataStructures

Bycomparingthequeuewiththe

binarytree,youcanseehowthe

structureofthedataaffectswhat

canbedoneefficientlywiththedata.


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Aqueueisagooddatastructureto

useforstoringthingsthatneedtobe

keptinorder,suchasasetof

documentswaingtobeprintedon

anetworkprinter.

.


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Thejobswillbeprintedintheorder

inwhichtheyarereceived.

Mostnetworkprintserversmaintain

suchaprintqueue.

.


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Abinarytreeisagooddatastructure

touseforsearchingsorteddata.

Themiddleitemfromthelistis

storedintherootnode,withlesser

itemstotheleYandgreateritemsto

theright.


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Asearchbeginsattheroot.The

computereitherfindthedata,or

movesleYorright,dependingonthe

valueforwhichyouaresearching.

Eachmovedownthetreecutsthe

remainingdatainhalf.


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Itemscanbelocatedveryquicklyinatree.

Telephonedirectoryassistance

informaonisstoredinatree,so

thatanameandphonenumbercan

befoundquickly.


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Lecture Outline

1

See the Access Database File (Lab1_Database_BBB.accdb) for this lectureon the course website !

Relational Databases Tables Columns Rows

Queries Query Design View Structured Query Language (SQL View)

Selecting rows meeting a condition Algebraic operations Text matching (with LIKE) Computing summary figures Joining multiple tables

Inserting, updating, and deleting data


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Databases: Overview

Overview what databases are, and what a databasemanagement system is.

Present key concepts and vocabulary. Demonstrate Microsoft Access and the BBB database.

BBB: Bookbinders Book Club We are using a reduced version, of a real database, for class

discussion

Full version exists

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Rationale

Why do we have databases? Because data are valuable and essential for conduct of business Because data are created in huge volumes, and need to be

retained (on disk) and efficiently accessed

Why do we have DBMSs? To manage the huge amounts of data and to facilitate use of these

data

Our focus will be on extracting data from databases inuseful ways. a.k.a. querying.

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RelaonalDatabases

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Last Name SS# DOB Major

Smith 100201122 06/11/84 IS

Kim 200202222 1/1/85 FIN

Davis 300201232 12/31/81 MKT

Pat 999132212 3/3/88 ACC

Student

Relational databases

Databases that use a series of logically related two-dimensionaltables to store their information

Tables are comprised of fields/records, which in turn contain fieldvalues

TableField

Record

Field value


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RelaonalDatabases

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Relational DatabaseTables

Records Fields

Field values

Bytes, bits

Last Name SS# DOB Major

Smith 100201122 06/11/84 IS

Kim 200202222 1/1/85 FIN

Davis 300201232 12/31/81 MKT

Pat 999132212 3/3/88 ACC

StudentTable

Field

Record

Field value


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Whydoweneedrelaonaldatabases?

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Problems arise when data is stored in one big file

Order# Date Customer ID Last Name First Name Address ISBN Book Name Author Price

1 9/1/03 C1001 Bezos Jeff 1 Amazon Plaza #0465039138 Code and other laws of cyberspace Lessig, Lawrence $25.00

2 9/2/03 C1004 Sproull LeeDean's Office, SternSchool, New York #1573928895

Digital Copyright: ProtectingIntel lectual Property on the Internet Litman, Jessica $55.00

3 9/3/03 C1002 Student Pat Tisch LC-12, New York #0072952849 MIS in the Information Age Haag, Stephen $98.75

4 9/4/03 C1003 Gates BillMicrosoft Corporation,Redmond #0738206679

Linked: The New Science ofNetworks

Barabasi, Albert-Laszlo $34.95

5 9/5/03 C1003 Gates BillMicrosoft Corporation,Redmond #0738206083

Smart Mobs: The Next SocialRevolution Rheingold, Howard $29.95

6 9/6/03 C1001 Bezos Jeff 1 Amazon Plaza #0738206083Smart Mobs: The Next SocialRevolution Rheingold, Howard $29.95

7 9/7/03 C1002 Student Pat Tisch LC-12, New York #1573928895Digital Copyright: ProtectingIntel lectual Property on the Internet Litman, Jessica $55.00

8 9/8/03 C1001 Bezos Jeff 1 Amazon Plaza #0738206083Smart Mobs: The Next SocialRevolution Rheingold, Howard $29.95


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Anomaliesinun-normalizeddata

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Insertion anomalies

Inability to insert a piece of information about an object thatcan exist independently of another object without having to

insert a piece of information about the other object

Example: Adding a new customer/book before it is orderedDeletion anomalies

The loss of a piece of information about one object when apiece of information about a different object is deleted

Example: Deleting an order => deleting a customer/bookUpdate anomalies

A need to change the same piece of information about an objectmultiple times

Example: Changing Bill Gates address


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AnormalizedversionofAmazonsdata

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Normalization

The process of assuring that a database can be implementedeffectively as a set of two-dimensional tables

Prevents insertion, deletion and update anomalies


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Benefits of Normalization

Greateroveralldatabaseorganizaon Minimizedataredundancies Dataconsistencywithinthedatabase Amoreflexibledatabasedesign Datacanbeusedmoreproducvely Abeerhandleondatabasesecurity

Disadvantage of Normalization

Reduced database performance because databasemust locate requested tables and join data - requiresadditional processing logic

A lot of Planning goes in to the design of a database


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Connecngtablestogether

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Primary keys

A field (or group of fields in some cases) that uniquely describeseach record in a table

Examples: Customer ID, ISBN, Order#Foreign keys

A field that is a primary key in one table and appears in adifferent table (though not as the primary key)

Examples: Customer ID in Orders

Integrity constraints

rules (most built in) that help ensure the quality of theinformation.

Not NULL


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Concepts & Terminology

Database: an organized collection of information about entities Sales, business transactions, personnel, inventory, products,

Entities have attributes. e.g. Person entity has attributes: Last Name, First Name, IDnumber,

Database management system (DBMS): a computerized record-keeping system.

DBMS: software for managing (creating, modifying, viewing, retrievinginformation, etc.) from databases.

Note: We focus on Relational DBMSs (RDBMs), the kind mostwidely used in business

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Let s Look at Microsoft Access

Microsoft Access: A RDBMS, part of the Microsoft OfficeProfessional suite, bundled with Word, Excel,

PowerPoint,

NOT an industrial strength DBMS Very useful for small applications, data analysis,

decision making

Works well with Excel; easy to use

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ACCDB files

Access 2007/2010 files end in .accdb Previous versions ended in .mdb One database = one .accdb file Access handles one database file at a time. Each database

consists of a number of tables.

In other databases, you might find one file per table, rather thanjust one file per database.

You will notice a temporary .laccdb file created whenever youopen your Access database: this is a lock file that prevents

problems when there is concurrent access by multiple users.

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Industrial Strength Databases

Different brands of RDBMSs: Commercial providers: Oracle, Microsoft SQL

Server, DB2, Sybase, Informix,Open Source (free): MySQL, PostgreSql,

All share a common view of things: tablesAll may be interacted with using SQL Knowledge of one directly transfers to all

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Launch Microsoft AccessOpen Lab1_Database_BBB.accdb

The database window: your portal into the database

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There are 6 tables in this database.

Double-click a table to open it.


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Relationships between tables

To explore the relationships between tables

Go to Database Tools tab Click on Relationships You will see an overview of tables and their

interconnections (see next slide)

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Relationships between Tables

Primary key forProduct table is ProdNum 33


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Concepts & TerminologyTables and Relationships

In an RDBMS, all records (all data) are kept in tables(a.k.a. relations).

A relation = A tableA relationship = A cross-reference between tables

The database consists of tables, each table having manyrows (a.k.a. records or tuples).

The 'Relationships View' of the database shows thetables and their attributes (columns), and the cross-

references between tables.

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Structure vs Contentof a Database Table

To view or edit the structure of a table: Right-clickit, then choose Design VieworTable Design

To view or edit the contents of a table: Double-clickit, or Right-clickit, then choose Open

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Structure of a TableDesign View of Customers Table (ACCTNUM is Key)

Primary key forCustomer table isAcctNum

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Concepts & TerminologyDesign View of a Single Table (e.g. Customers)

Every table is made-up of attributes

Every attribute has a data type Every table has a primary key: one or more attributes

whose values uniquely identify each table record.

Primary keys are shown with a key icon in Design View

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Contentsof a Database Table

If in Design View, and you want to view or edit thecontents of the table:

Choose Datasheet Viewfrom the Design tab

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Data in the TableA Portion of the Customer Table

Records (rows) Attributes (columns) Fields (row elements or "cells"). 39


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Design View of Purchase

A two-attribute primary key: ACCTNUM and CAMPNUM Details of primary key assignment and database design are

beyond the scope of this course.

Typically, though, it is best to create a single, system generated(auto-incremented) column, that uniquely identifies each row.

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Indexesto improve performance

To improve the performance of yourdatabase queries, you should create

indexes on any columns that are

regularly looked up.

Creating an index is easy: simplyindicate Indexed asYes in the settings

for the column in Design view.

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Key Points

Tables: hold all data in a database Rows = records Columns = attributes Attributes: have a data type (number, text, date, etc.) Fields: at the intersection of a row and a column Primary Keys: attributes whose values uniquely refer to any

given row in a table

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Single-Table Queries: Overview

Querying single tables: Intuitions Microsoft Access Query Design View SQL Microsoft SQL-details

Database design intuitions(Why split one table into many small ones)

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Querying single tables

Table structureAttributes (columns)

Records (rows)

Column order and row order do not matter Queries subdividing a table

Pick the table you want to look at Pick the column(s) you wish to see

Pick the row(s) you wish to see

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Querying single tables

BBB Customers:

What data do we have about customers Name (first, middle, last)Address (street num, street, city, state, zip) Demographics (gender, money non-book purchases)

What do we want to know

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Querying single tables: Intuitions

Names of all male customers

ACCTNUM FIRSTNAME

MIDDLEN

AME FAMILYNAME

STREET

NUMBER STREET CITY STATE ZIP GENDER MONEY

13015 DENNIS N SKRYPEK 1260 34th AV PRT WASHINGTN NY 11050 M 164

13016 LOIS T ENGLANDER 105 9th ST WILLINGBORO NJ 8046 F 254

13017 JANET SIECK 767 3rd ST FOXBORO MA 2035 F 169

13018 ANN A MARUZZI 1948 10th ST TEWKSBURY MA 1876 F 65

13971 SAMUEL E HAYES 382 7th ST CENTERVILLE PA 16404 M 81

14200 EARL J TUCHMAN 1707 29th ST LAKEWOOD NJ 8701 M 135

17640 AUDREY S KAUFFMANN 1002 RICHMOND HILL AV WEST ORANGE NJ 7052 F 236

17641 DOROTHY VACCHER 1751 17th AV BROOKLYN NY 11234 M 68

17642 SANDRA M POSNOCK 1016 MOON AV RIDGWAY PA 15853 F 180

17643 GERALD C CANNON 1841 2nd AV LEXINGTN MD 20653 M 159

17644 BETTY K DEL 1794 MARIA ST MULLICA NJ 8062 F 112

17645 LYNN HUEBBERS 1357 14th AV ANDOVER MA 1810 F 41

17646 MARY C TALLUTO 1861 2nd ST NEPTUNE NJ 7753 F 102

19630 CATHERINE R CASANO 965 7th ST SCRANTON PA 18503 F 209

19631 EDITH E WISCHHUSEN 1520 1st ST PITTSBURGH PA 15243 F 89

19632 KIMBERLY A SCHOENBERG 1081 18th ST KINGSVILLE MD 21087 F 262

19633 MARILYN FLAHERTY 33 24th AV WARREN NJ 7059 F 17019634 JOSEPH L FAIELLA 1322 4th AV CLEVERDALE NY 12820 M 200

19635 ROBERT A SANDLER 316 18th ST PHILADELPHIA PA 19148 M 93

23088 JAMES M MILLER 409 11th AV SPRING NY 10977 M 63

23089 PATRICIA WERNER 1535 MARIS ST LONG BEACH NY 11561 F 137

23090 MARY J MILLER 379 5th ST FRAMINGHAM MA 1701 F 50

23360 CATHERINE J IMPERATORE 1671 24th ST BROOKLYN NY 11226 F 187

23361 HARRIET A FAILLA 140 JAMES ST REHOBOTH DE 19971 F 190

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Querying single tables: IntuitionsNames of all male customers

FIRSTNAME

MIDDLE

NAME FAMILYNAME

DENNIS N SKRYPEKSAMUEL E HAYES

EARL J TUCHMAN

DOROTHY VACCHER

GERALD C CANNON

JOSEPH L FAIELLA

ROBERT A SANDLER

JAMES M MILLER

!

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Querying single tables: Intuitions

Query variations on single tables:1. Pick attributes (columns)2. Pick records (rows) specifying a single condition

(e.g. Pick all rows where Gender = 'M')

3.

Pick rows using two or more conditions4. Selecting rows with attributes you do not display5. Using string matches to pick rows6. Renaming an attribute (column) name7. Arithmetic operations in a query8. Sorting the output (ordering the rows)9. Mathematical aggregations in a query

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Querying single tables:Microsoft Access Query Design View

Go to the Create tab Choose eitherQuery WizardorQuery Design Pick one table (for querying single tables) Pick the columns you want to retrieve, and specify the criteria for the

rows you want to retrieve. Once in Query Design view, choose Design tab, then Run (! button on

the toolbar) OR Datasheet Viewto see your query results.

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Query Wizard

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Query Wizard

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Press > button to select columns one at a time.Press >> button to select all columns.

Specify which table your data is in.


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Query Wizard

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Choose Detailto retrieve individual rows that meet certain criteria.Choose Summaryto compute aggregates (e.g. min, max, average, ..)


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Query Wizard

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Name your query, so that you can save it and view / modify it later


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Query Design View

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Select the Table you want to query, then pressAddthe button.

Press Done button when finished.


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Query Design ViewSelecting Columns

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Double-click the columns you want to include in your query,or drag-and-drop them from the table into the grid view at the bottom

Double-click * to include them all


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The grid view at the bottom shows you whether the column is visible (tickShow row). It also lets you specify filter conditions, using the Criteria row.


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View the query results

Choose whether you want to: View data (SELECT) Insert a table (MAKE) Insert a row (APPEND) Edit a row (UPDATE) Produce aggregate reports (CROSSTAB) Remove rows of data (DELETE)

Show tables, so you can add morecolumns to your query results.


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Viewing Saved Queries

Click on the down arrow to the right of the Tables heading in thedatabase view Then choose Queries

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Query Design ViewQuery 1: Picking attributes (columns)

Drag and drop

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Query Design ViewViewing the query results

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Query Design ViewSaving the query

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Right-click in the title bar for the QueryThen choose Save from the pop-up menuChoose an intuitve and descriptive name (e.g. Names of our customers )


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Viewing Saved Queries

After you save the SELECT query, it will

look like this in the query list on the left

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Query Results ViewSwitching back to the query design

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Query Design ViewMaking a copy of a query

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Right-click in the Query list on the left Choose Copy Right-click again, and choose Paste Choose an intuitive name for your new query


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Query Design ViewQuery 2: Picking records (rows)

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Drag and drop your criterion into the grid Specify the filter condition (e.g. = PA )


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Query Design ViewQuery 2: Picking records (rows)

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Now press Run or press DataSheet View to view your results Notice how the results only include customers who live in Pennsylvania (PA)


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Query Design ViewQuery 3.1: Picking rows with two conditions - AND

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Here there are no records satisfying both conditions.

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The ACCTNUM column is numeric,so specifying a string condition causes a data type mismatch error..


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Query Design ViewQuery 3.3: Picking rows with two conditions - OR

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Query Design ViewQuery 3.3: Picking rows with two conditions - OR

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Query Design ViewQuery 4: Picking rows using attributes you do not display

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Uncheck the Showbox if you don t want to show the column in your results


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Query Design ViewQuery 4: Picking rows using attributes you do not display

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Notice that the customers Last Name is not shown, because we unchecked theShowbox for Last Name in the Query Design View in the previous slide.

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Query Design ViewQuery 5: Using string matching to pick rows

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You must use the keyword LIKE if you use a wildcard (e.g. * or ?).If you forget LIKE the database will look for an actual * or ?

and you won t get the matches you wanted !!

LIKE means match wildcards The wildcard * means match

any number of characters

So LIKE *IL* means find anystrings that have IL anywhere

inside them. That is, anythingbefore IL and anything after.

You can also use ? to match asingle character

In most other databases: use % instead of * use _ instead of ?


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Notice here we have all customerswhose familyname has 'IL' in the middle of the string

Query Design ViewQuery 5: Using string matching to pick rows

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Query Design ViewQuery 6: Renaming an attribute (column) name

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[New column name] : [Old column name]


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New column name appears in results,in place of old column name.

Query Design ViewQuery 6: Renaming an attribute (column) name

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Query Design ViewQuery 7: Arithmetic operations in a query

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Simply type the formula in the Field row.No loops or VBA code are necessary.


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Query Design ViewQuery 7: Arithmetic operations in a query

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SQL is called a declarative language, because we tell thedatabase what we need, rather than how to get it, and the

database gets the result in the most efficient way possible.There is no need to write loops.

In contrast, VBA is a procedural language: we have to writeloops to tell VBA exactly how to get the data we want.

Procedural languages are far more verbose, and require

more code to get the same job done.


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Query Design ViewQuery 8: Sorting the output (ordering the rows)

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Query Design ViewQuery 8: Sorting the output (ordering the rows)

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Notice our results are now sorted by Tax,from highest to lowest

Query Design View


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Query Design ViewQuery 9.1: Mathematical aggregations

Average for all customers

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Other aggregate functions:Min, Max, Count,

See the Query Design Wizard.

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We can see the average Moneyfor all customers in the data set

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Average for a subset of customers

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Aggregatefunction returns

one row.

Non-Aggregatecriterion returns

multiple rows.

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Aggregatefunction returns

one row.

Non-Aggregatecriterion returns

multiple rows.

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Solution: Donot show the

non-aggregatefilter condition

column. Thatwill fix the error.

Query Design View


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We can see the average Moneyfor all customers in Pennsylvania

Query Design View


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Average for each group of customers

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Groupcustomers by

state.

Sort by averagemoney spent for

the state.

Query Design View


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We can see the average money spent forcustomers in each state,

and we ve sorted by average money so we caneasily see which are most lucrative states are.

Query Design View


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Query Design ViewBuilding Complex Expressions

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Right-click in the Field row.Then choose Build to build a more complex expression.


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SQLGeneral query framework

SQL is the language underlying Microsoft Access, and

is the query language standard used by all major RDBMS

SELECT in the order you want to see them

FROM

[WHERE]

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Editing SQL

Just like "Editing a recorded VBA Macro:

Write a query using Query Design View and then edit using SQL Viewor

Open the SQL View from a new query and write in SQL from scratch

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SQL View


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SQL ViewViewing the SQL underlying

all your graphical query designs

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For any query, you can view theSQL that Microsoft Access wrote

for you, by simply choosing Viewand then SQL View.

Editing the SQL directly is quicker

and more powerful, so expert

users tend to use SQL view,whereas novices tend to use the

Graphical Design view.


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SQLQuery 1: Picking attributes (columns)

SELECT ACCTNUM, FAMILYNAME, STATE

FROMCUSTOMER

SELECT STATE, ACCTNUM, FAMILYNAMEFROMCUSTOMER

Attribute order does not matter

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SQLQuery 2: Picking records (rows)


FROMCUSTOMER

WHERE STATE = 'PA'

Order of rows in output does not matter, and is not necessarily predictable

ACCTNUM FAMILYNAME STATE17642POSNOCK PA19630CASANO PA19631WISCHHUSEN PA19635SANDLER PA50670KEYSER PA

ACCTNUM FAMILYNAME STATE19630CASANO PA50670KEYSER PA17642POSNOCK PA19635SANDLER PA19631WISCHHUSEN PA

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SQL


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SQLQuery 3.1: Picking rows with two conditions - AND


FROMCUSTOMER

WHERE STATE = 'PA'

AND FAMILYNAME = 'MILLER'

SELECT acctnum, familyname, state

FROMcustomer

WHERE state = 'PA'

and familyname = 'Miller'

SELECT acctnum, familyname, state

FROMcustomer

WHERE state = 'PA'

AND familyname = 'MILLER'

SQL is case sensitive within quotes Microsoft Access is NOT

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SQLQuery 3.2: Picking rows with two conditions - AND

Remember that all attributes have a datatype


FROMCUSTOMER

WHERE STATE = 'PA'

AND ACCTNUM = 'MILLER'

ACCTNUM is a NUMBER

MILLER is a STRING

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SQ


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SQLQuery 3.3: Picking rows with two conditions - OR


FROMCUSTOMER

WHERE STATE = 'PA'

ORFAMILYNAME = 'MILLER'


FROMCUSTOMER

WHERE STATE = 'PA'

AND (FAMILYNAME = 'MILLER'ORFAMILYNAME = 'SMITH')

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SQLQuery 4: Picking rows using attributes you do not display

SELECT ACCTNUM, STATE

FROMCUSTOMER

WHERE STATE = 'PA'

ORFAMILYNAME = 'MILLER'

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SQL


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SQLQuery 5: Using string matching to pick rows*


FROMCUSTOMER

WHERE STATE = 'PA'

AND FAMILYNAME LIKE '%IL%'

SELECT ACCTNUM, FAMILYNAME, STATEFROMCUSTOMER

WHERE STATE = 'PA'

AND FAMILYNAME LIKE 'IL%'

SELECT ACCTNUM, FAMILYNAME, STATEFROMCUSTOMER

WHERE STATE = 'PA'

AND FAMILYNAME LIKE '_IL'

Standard SQL notation shown above Microsoft Access notation differs as shown

% matches anynumber of

characters(Use * in Access)

_matches any onecharacter

(Use ? in Access)

SQL


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SQLQuery 6: Renaming an attribute (column) name

SELECT ACCTNUM, FAMILYNAMEAS Last_Name, STATE

FROMCUSTOMER

WHERE STATE = 'PA'

AND FAMILYNAME LIKE '*IL*'

SELECT ACCTNUM, FAMILYNAMEAS [Last Name], STATE

FROMCUSTOMER

WHERE STATE = 'PA'

AND FAMILYNAME LIKE '*IL*'

Bracket notation to allow white-space is unique to Microsoft

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SQLQuery 7: Arithmetic operations in a query

SELECT ACCTNUM, FAMILYNAMEAS Last_Name,

MONEY * 0.10 AS Taxed_Expense

FROMCUSTOMER

WHERE FAMILYNAME LIKE '*IL*'


(MONEY + ACCTNUM)*1.09 AS Random_nonsense

FROMCUSTOMER

WHERE FAMILYNAME LIKE '*IL*'

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SQL


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SQLQuery 8: Sorting the output (ordering the rows)



FROMCUSTOMER

WHERE FAMILYNAME LIKE '%IL%'

ORDER BY FAMILYNAMEASC



FROMCUSTOMER

WHERE FAMILYNAME LIKE '%IL%'

ORDERBY Last_Name DESC

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You must use the originalcolumn name in your ORDER BY

clause.

Use ASC for Ascending order orDESC for Descending order.

If you use the new columnname, it won t work.

SQL


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SQLQuery 9.1: Mathematical aggregations


SELECTAVG(MONEY)AS Average_Expense

FROMCUSTOMER

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SQL


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Query 9.2: Mathematical aggregations


SELECTAVG(MONEY)AS Average_Expense, STATE

FROMCUSTOMER

WHERE STATE = "PA"

SELECTAVG(MONEY) AS Average_Expense, STATE

FROMCUSTOMER

Be careful when selecting both aggregations and ordinary attributes

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SQL


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Query 9.2: Mathematical aggregations


SELECT AVG(MONEY)AS Average_Expense, STATE

FROMCUSTOMER

WHERE STATE = "PA"

Be careful when selecting both aggregations and ordinary attributes

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SQL


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QQuery 9.3: Mathematical aggregations


SELECT

Avg(CUSTOMER.[Money])AS [Average Money],

CUSTOMER.State

FROMCUSTOMER

GROUP BY CUSTOMER.State

ORDER BY Avg(CUSTOMER.[Money]) DESC;

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Microsoft Flavored SQL

Attribute names in the SELECT clause are prefaced by table name(e.g. CUSTOMER.ACCTNUM)

Use of the * versus % in matching multiple characters in LIKEexpression

Use of ? Versus _ in String matching single character in LIKEexpression

Use of [ ] in renaming to allow white spacese.g. CUSTOMER.FAMILYNAME AS [Last Name]

Case sensitivity(Microsoft Access is case insensitive e.g. State = "PA" vs. State = "pa")

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WARNING


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Case Sensitivity in SQL

SELECT * FROMCUSTOMER

WHERE UPPER(STATE) = PA

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Text in Microsoft Access is not case-sensitive.However, many other databases are case-sensitive.

To avoid problems with case-sensitivity in SQL

queries, use the UPPER() function, to convert the

text to uppercase, before using it !

K P i t


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Key Points

Querying is simple Pick the table Pick the columns Pick the rows (using some simple or complex criteria)

Create queries just like VBA Macros Begin in Query Design View; Edit in SQL View Write queries in SQL View from scratch

Nine (9) simple cases were given as examples. Be wary of exceptions (e.g. SELECT AVG(MONEY), STATE)

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Multi-Table Queries:


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Multi Table Queries:

Overview

Database design intuitions(Why split one table into many small ones)

Querying two tables Intuitions SQL Microsoft Access Query Design View

Microsoft SQL-details

Querying more than two tables112

Laying out Data in a Single


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y g g

Spreadsheet TableSort by product

PRODNAME CATNAME PRICE CAMPDATE CHANNAME

ACCT

NUM QTY PURCHDATE

CAR MAINTANANCE DO-IT-YOURSELF 15 12/1/1987 2 MIN TV SPOT ESPN 13971 1 1/21/1988

14200 1 1/8/1988

42763 1 1/13/1988

SECRETS OF FRENCH COOKING COOK 15 12/1/1986 "ROCK STARS" - MAG 13018 1 1/26/1987

19635 1 1/9/1987

23361 1 1/22/198725508 1 1/26/1987

27028 1 1/20/1987

27259 1 1/22/1987

34652 1 1/23/1987

39403 1 1/18/1987

50670 1 1/26/1987

58775 1 1/11/1987

2/1/1987 2 MIN TV SPOT ESPN 17646 1 3/8/1987

23088 1 3/20/198732698 1 3/18/1987

44985 1 3/16/1987

54690 1 3/20/1987

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y g g

Spreadsheet TableSort by channel


ACCT

NUM QTY PURCHDATE



2/1/1987 2 MIN TV SPOT ESPN 17646 1 3/8/1987

14200 1 1/8/1988

42763 1 1/13/1988

19635 1 1/9/198723361 1 1/22/1987

25508 1 1/26/1987

27028 1 1/20/1987

27259 1 1/22/1987

34652 1 1/23/1987

39403 1 1/18/1987

50670 1 1/26/1987

58775 1 1/11/1987

23088 1 3/20/1987

32698 1 3/18/1987

44985 1 3/16/1987

54690 1 3/20/1987

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S


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Spreadsheet TableFilling out the table


ACCT

NUM QTY PURCHDATE














SECRETS OF FRENCH COOKING COOK 15 2/1/1987 2 MIN TV SPOT ESPN 17646 1 3/8/1987SECRETS OF FRENCH COOKING COOK 15 2/1/1987 2 MIN TV SPOT ESPN 23088 1 3/20/1987

SECRETS OF FRENCH COOKING COOK 15 2/1/1987 2 MIN TV SPOT ESPN 32698 1 3/18/1987



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Database Design


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Database DesignSplitting tables

Products Campaign

Category

CAT

NUM CATNAME

1 CHILDREN

2 YOUTH

3 COOK

4 DO-IT-YOURSELF

5 REFERENCE

6 ART

7 GEOGRAPHY

Channels

CHAN

NUM CHANNAME

3 2 MINUTES SPOT - TV - ESPN (SPORT CHANNEL)

4 2 MINUTES SPOT - TV - MTV (MUSIC CHANNEL)6 ADVERTISING IN LOCAL NEWSPAPERS

13 "ROCK STARS" - MAGAZINE

PRODNUM PRODNAME

CATNUM

2PINNOCCHIO 121SECRETS OF FRENCH COOKING 3

31CAR MAINTANANCE 433GARDENING 4

1ALICE IN WONDERLAND 1

CAMPNUM

PRODNUM PRICE CAMPDATE

CHANNUM

21 21 15 12/1/1986 13221 21 15 2/1/1987 3201 1 15 2/1/1987 4

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Database Design


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Database DesignSplitting tables (cont)

ACCT

NUM

CAMP

NUM QTY PURCHDATE

13018 21 1 1/26/1987

19635 21 1 1/9/1987

23361 21 1 1/22/1987

25508 21 1 1/26/1987

27028 21 1 1/20/1987

27259 21 1 1/22/1987

34652 21 1 1/23/1987

39403 21 1 1/18/1987

50670 21 1 1/26/1987

58775 21 1 1/11/1987

17646 221 1 3/8/1987

23088 221 1 3/20/198732698 221 1 3/18/1987

44985 221 1 3/16/1987

54690 221 1 3/20/1987

13971 1231 1 1/21/1988

14200 1231 1 1/8/1988

42763 1231 1 1/13/1988

Purchase

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Database Design


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Go to Database Tools table and click Relationships button to view this118

Database Design


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Avoid repetition within individual tables Separate attributes that are used independently into

separate tables

Introduce (foreign) keys to link tables and keep anyredundancy minimal/simple

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Querying two tables


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Querying two tables

Table structure Attributes (columns) Records (rows)

Column order and row order do not matter

Queries combine and then subdivide Pick two tables that you want to look at Combine the two tables (Cartesian product) Pick the row(s) you wish to see Pick the column(s) you wish to see

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Querying two tables


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Querying two tables

BBB Customers and Purchases

What data do we have about customers

What data do we have about purchases Who purchased (Acctnum) In response to what advertising campaign In what quantity When did they purchase

What do we want to know e.g. Find responses by customers to campaigns

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Querying two tables


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Customer response (purchases) to campaigns

ACCT

NUM

CAMP

NUM QTY PURCHDATE

13018 21 1 1/26/1987

19635 21 1 1/9/198723361 21 1 1/22/1987

Customer (truncated to fit on the slide)

Purchase

ACCT

NUM FIRSTNAME STATE ZIP GENDER MONEY

13015 DENNIS NY 11050 M 164

19635 ROBERT PA 19148 M 93

23361 HARRIET DE 19971 F 190

Step 1.Pick two tables

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Querying two tables


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Customer response (purchases) to campaigns

ACCT

NUM

CAMP

NUM QTY PURCHDATE

13018 21 1 1/26/1987

19635 21 1 1/9/198723361 21 1 1/22/1987

Customer (truncated to fit on the slide)

Purchase

ACCT


13015 DENNIS NY 11050 M 164

19635 ROBERT PA 19148 M 93

23361 HARRIET DE 19971 F 190

Step 2.Combine the two tables(Cartesian Product i.e. every

row from first table combined, inturn, with every row from second)

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Querying two tables


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ACCT

NUM

CAMP

NUM QTY PURCHDATE

ACCT


13018 21 1 1/26/1987 13015 DENNIS NY 11050 M 164

y gCustomer response (purchases) to campaigns

ACCT

NUM

CAMP

NUM QTY PURCHDATE

13018 21 1 1/26/1987

19635 21 1 1/9/1987

23361 21 1 1/22/1987

CustomerPurchase

ACCT


13015 DENNIS NY 11050 M 164

19635 ROBERT PA 19148 M 93

23361 HARRIET DE 19971 F 190

continue for all permutations of

Purchase and Customer records

13018 21 1 1/26/1987 19635 ROBERT PA 19148 M 93

13018 21 1 1/26/1987 23361 HARRIET DE 19971 F 190

124

Querying two tables


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y gCustomer response (purchases) to campaigns

ACCT

NUM

CAMP

NUM QTY PURCHDATE

13018 21 1 1/26/1987

19635 21 1 1/9/1987

23361 21 1 1/22/1987

CustomerPurchaseACCT


13015 DENNIS NY 11050 M 164

19635 ROBERT PA 19148 M 93

23361 HARRIET DE 19971 F 190

PURC.

ACCT

NUM

CAMP

NUM QTY PURCHDATE

CUST.

ACCT


13018 21 1 1/26/1987 13015 DENNIS NY 11050 M 164

13018 21 1 1/26/1987 19635 ROBERT PA 19148 M 93

13018 21 1 1/26/1987 23361 HARRIET DE 19971 F 190

19635 21 1 1/9/1987 13015 DENNIS NY 11050 M 164

19635 21 1 1/9/1987 19635 ROBERT PA 19148 M 93

19635 21 1 1/9/1987 23361 HARRIET DE 19971 F 190

23361 21 1 1/22/1987 13015 DENNIS NY 11050 M 164

23361 21 1 1/22/1987 19635 ROBERT PA 19148 M 93

23361 21 1 1/22/1987 23361 HARRIET DE 19971 F 190

Step 3.Pick some rows:Purchase.Acctnum = Customer.Acctnum

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Querying two tables


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Que y g t o tab esCustomer response (purchases) to campaigns

PURC.

ACCT

NUM

CAMP

NUM QTY PURCHDATE

CUST.

ACCT

NUM FIRSTNAME STATE ZIP G ENDER MO NEY

13018 21 1 1/26/1987 13015 DENNIS NY 11050 M 164

13018 21 1 1/26/1987 19635 ROBERT PA 19148 M 93

13018 21 1 1/26/1987 23361 HARRIET DE 19971 F 190

19635 21 1 1/9/1987 13015 DENNIS NY 11050 M 164

19635 21 1 1/9/1987 19635 ROBERT PA 19148 M 93

19635 21 1 1/9/1987 23361 HARRIET DE 19971 F 190

23361 21 1 1/22/1987 13015 DENNIS NY 11050 M 164

23361 21 1 1/22/1987 19635 ROBERT PA 19148 M 93

23361 21 1 1/22/1987 23361 HARRIET DE 19971 F 190

PURC.

ACCT

NUM

CAMP

NUM QTY PURCHDATE

CUST.

ACCT


19635 21 1 1/9/1987 19635 ROBERT PA 19148 M 93

23361 21 1 1/22/1987 23361 HARRIET DE 19971 F 190

Step 4.Pick some columns

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Querying two tables: The final result


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Querying two tables: The final resultCustomer response (purchases) to campaigns

CAMP

NUM QTY

ACCT

NUM GENDER

21 1 19635 M

21 1 23361 F

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SQL


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SQLGeneral JOIN framework: two tables

SELECT

in the order you want to see them

prefix attributes with tablename e.g. table1.attr1

FROM ,

WHERE

You must cross-reference (i.e. join) therelated columns in the tables, using

table1.columnA = table2.columnA

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SQL


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Customer responses to campaigns (i.e. customer purchases)

SELECT CAMPNUM, QUANTITY,

CUSTOMER.ACCTNUM, GENDER

FROMPURCHASE, CUSTOMERWHERE PURCHASE.ACCTNUM = CUSTOMER.ACCTNUM

129

Notice how, unlike VBA, no line-continuation character is used in SQL

SQL


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Customer responses to campaigns (i.e. customer purchases)

130

If you make a spelling mistake in your query, you ll get an (error)message like the one shown below

SQL


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SQLA nonsense query for example purposes

SELECT CAMPNUM, PRICE, ACCTNUM

FROMCAMPAIGN, CUSTOMER

WHERE PRICE > MONEY

ORFIRSTNAME LIKE 'ROB%'

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Query Design View


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Query Design ViewQuerying two tables

Two cases using Microsoft Access Query Design View:

1. If both tables have a key attribute with the same name(e.g. PURCHASE and CUSTOMER both have anattribute called ACCTNUM), then Microsoft Access willautomatically create the join.

2. In all other circumstances, you must manually specifythe join:

the tables have attributes with the same name, but one or bothare not designated as key attributes

the key attributes in different tables do not have the samename

the tables have no shared attributes whatsoever132

Query Design ViewFinding all purchases by customers:


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Finding all purchases by customers:

Picking our tables

133

PressShift + Click

to selectmultiple tables,

and press theAdd button.

Press Close

button when

done.

Query Design View


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Case 1: Key attribute with same name

134

Drag and drop your columns into the grid In this case there is no need to explicitly say:

Customer.AcctNum = Purchase.Acctnumbecause Microsoft Access is intelligent enough to

infer the relationship between the tables automatically

Query Design View: Results of QueryC 1 K tt ib t ith


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135

This result isn t very readable

Campaign number doesn t mean much:Product name (from the Product table)would be more descriptive

Account number doesn t mean much:Customer name (from the Customer table)

would be more descriptive

SQL ViewCase 1: Key attribute with same name


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136

Microsoft Access generates some pretty nasty looking SQL:

You can actually simplify it to this:

Query Design ViewCase 2: No shared attributes


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Case 2: No shared attributes

Finding all products purchased by customers

137

The Customer and Product tables are notdirectly related, so Microsoft Access is

unable to infer the relationship.

Query Design ViewCase 2: No shared attributes


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Case 2: No shared attributes

Finding all products purchased by customers

138

To find the relationship betweenCustomers and Products:

Go to Show Tables, then Select Purchase and Campaign tables,

which link Customer to Product PressAddbutton Notice the relationships now visible


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Querying more than two tables

Example 1:

What products did each customerpurchase?

139



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Querying more than two tablesWhat products did each customerpurchase?

140



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y gFollowing the Yellow Brick Road

141



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Querying more than two tablesWhat products did each customerpurchase?

142



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Querying more than two tablesWhat products did each customer purchase?

143



Querying more than two tables: ResultsWhat products did each customer purchase?


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What products did each customer purchase?

144

To confirm you have the correct number of results, check that you have thesame number of rows here as there are in the PURCHASES table.

There were 19 purchases, so there should be 19 results here !

Querying more than two tables: ResultsWhat happens if you forget the join / cross-reference?


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145

Notice that you get an impossible number of results if you forget the JOIN inthe query: i.e. if you forget to specify which columns cross-reference !

There were 19 purchases, so there should be 19 results here !


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Example 2:

What channels was each product advertised on ?

146



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Q y gWhat channels was each product advertised in ?

147



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y gWhat channels was each product advertised in ?

148

Querying more than two tablesWhat channels was each product advertised in ?


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What channels was each product advertised in ?

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150



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151





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152

The results of the query :

To confirm you have the correct number ofresults, check that you have the same

number of rows here as there are in theCAMPAIGN table. There were 3 campaigns,

so there should be 3 results here !



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y g

Option 1: Create one giant table

Create one giant table (Cartesian Product)A B C D

Option 2: Combine tables pair-wise

Associative: (A B) C = A (B C) Combine in stages. For three or more

A B (A B) C ((A B) C ) D

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Key Points


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y

Divide tables for ease in managing data Query two (or more) tables like one big table

Combine tables: Cartesian Product Put tables side-by-side: every row permutation Look for attributes that link tables

(e.g. Acctnum in CUSTOMER and PURCHASES)

Create queries just like VBA Macros Begin in Query Design View; Edit in SQL View, or Write queries in SQL View from scratch

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Inserting, Updating, and Deleting Data


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When you open Access, you must click Options

on the message bar, and choose Enable this content, if you want

SQL INSERTs, UPDATES, and DELETES to work!

155

Inserting Data


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Use the INSERT statement to append new data.

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Here are the various parts of the INSERT statement:

INSERT INTO [table-name] ( [ column1, column2,

] )VALUES ( [value for column1], [value for column2],);

Inserting Data


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Use the INSERT statement to append new data.

157

Inserting Data


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After you save the INSERT query, it willlook like this in the query list on the left

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Updating Data


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Use the UPDATE statement to edit existing data.

159

Here are the various parts of the UPDATE statement:

UPDATE [table-name]

SET [column1] = [value], [column2] = [value],

WHERE [column] = [value]

DON T FORGET YOUR WHERE CLAUSE !! IF YOU FORGET IT YOU COULD

END UP MISTAKENLY UPDATING ALL DATA IN THE TABLE ! Access 2007will give you a warning if you inadvertently update multiple rows, but, if you

execute the UPDATE statement from Excel 2007, you ll get no such

Updating Data


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Use the UPDATE statement to edit existing data.

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Updating Data


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After you save the UPDATE query, it willlook like this in the query list on the left

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NOTE:It is often bad practice to update data in a database.

For example, rather than update a customer s address, you can add an

event table e.g. a table called MOVE with a date the customer moved.That way you always have an audit log of when the customer moved,

and you have not lost any data.

You might, for instance, later want to count how many times the customer

moved in the past 3 years, so you can compute a credit score for them.

Deleting Data


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Here are the various parts of the DELETE statement:

DELETE FROM [table-name]

WHERE [column] = [value]

DON T FORGET YOUR WHERE CLAUSE !! IF YOU FORGET IT YOU COULD

END UP MISTAKENLY DELETING ALL DATA IN THE TABLE ! Access 2007 willgive you a warning if you inadvertently delete multiple rows, but, if you

execute the DELETE statement from Excel 2007, you ll get no such warning,

and it will be impossible to recover the data you have deleted !!

Use the DELETE statement to permanently remove a row of data.

162

Deleting Data


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Use the DELETE statement to permanently remove a row of data.

163

Deleting Data


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After you save the DELETE query, it willlook like this in the query list on the left

164

NOTE:It is generally bad practice to delete data from a database.

Rather, you want to add a column, and mark the data as inactive

(include a column with the date it was marked inactive and

a column with the user-ID of the user who marked it as inactive, if necessary).

That way you always have an audit log of when data was deleted ,

and you can always recover the data later.

Obtaining Data via Email


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Microsoft Access 2007 contains great new features

to allow you to collect data via email.You need to have Microsoft Outlook 2007 installed and working.

Click on External Data tab in Access 2007.

Then click on Create Email.


A wizard will help you through the process of composing your


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166

p y g p p g y

electronic data collection form.


Recipients will need to have an HTML-capable email client, to be able to


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167

respond to your emails. Luckily, most people have one nowadays.


Specify what you would like to do with the data.


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p y y

Obtaining Data via EmailSpecify which fields (database columns)

t t i l d i il


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169

you want to include in your email.


Specify how you want to hand replies.


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Obtaining Data via EmailSet automatic processing options.

Y h t li t ti ll t ll dd li t


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You can choose to process replies automatically, or to manually add replies to

the database after you have checked each individually in Outlook.


Select how you want to specify the email addresses of recipients.


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If your email addresses are in your database, specify whether the

dd i th t t bl i li k d t bl


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addresses are in the current table, or in a linked table.


Specify the contents of the email you are sending.


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Confirm the email addresses of the message recipients.


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After sending your email wait for some responses then click


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After sending your email, wait for some responses, then click

Manage Replies to manage your responses.


Under Manage Replies, you can choose to resend the email, if it wasnt

sent successfully the first time


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sent successfully the first time.

Lab Exercise


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17

Our next session will be a

Databaseslab exercise

ROOM JMHH 380


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17

CREDITS: Alan Abrahams, VA Tech

S2:DataStructuresandSQL


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ShawndraHillS i 2013

Date post:	04-Apr-2018
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