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Week 1 - Database Introduction Data What is data? - Raw, Raw, unpr unproc oces esse sed d fac facts ts and and figu figure res s Data Vs. Information - Data Data are are the ‘buid ‘buiding ing boc!s" boc!s" of inform informati ation on - Information Information is data data that that is processed, processed, organi organised, sed, structured structured or prese presented nted in a gi#en conte$t so as to ma!e it usefu - Informa Informatio tion n is data data with with a specif specific ic meani meaning ng associ associate ated d with with it - %igh %igh &uait &uaity y infor informat mation ion is !ey !ey to to decis decision ion ma!ing ma!ing - Data Data ' (ro (roces cessi sing ng here here ' Inf Infor orma mati tion on )rgani*ationa Resources +uccess depends on efficient use of resources - oney - %uman capita - /echni chnica ca !no !now-h w-how !is, !nowedge, e$perience, etc. o - Data - Infrastructure 0uidings, factories, e&uipment, etc. o Vaue of Data - 1orp 1orpor orat ate e dec decis isio ions ns dep depen end d on on dat data a Day-to-day transactions o 1ustomer data, sur#eys o %istorica data o ar!et pricestrends, effect of promotions, saes datatrends What are the issues customers compain about the most? Which promotions generated the most profit? What is most effecti#e time period for a promotion? - 3o 3oss ss of data data imp impie ies s os oss s of of mon money ey 1orporate Data 1yce
4$ampe +5ma*on.com - /ries /ries to to predict predict other other items items a customer customer may may want want to purchase purchase based based on on what"s in their shopping cart and the purchasing beha#iors of other customers based on historica data ' infuence buyer beha#iour
Infosys 222 Why Data atters? - https6 https6www www.yo .youtu utube.c be.com omwa watch? tch?#7f #7f289 289i2: i2:;<< ;<<= = 4ssentia features of Information - /imey - 5ccurate - 1ompete 4$ercise - 4$ampe 4$ampe o off using using Datain Datainforma formation tion for decision decision ma!ing in a specific specific Industry Industry
Database and Database Management System (DBMS) What is database? - tru truct ctur ured ed coe coect ctio ion n datai datainf nfor orma mati tion on - 4$am 4$amp pe6 e6 e ear arch chin ing g Dat Datab abas ase e Database characteristics - Database Database +digita +digitasoft software ware is is typicay typicay a shared, shared, integrat integrated ed computer computer structure housing 4nd-user data o
o
etadata
What is Database anagement ystem +D0? - pecia pecia softwa software re desi designe gned d to hep hep manag manage e the the datab database ase - Databas Database e system system can be be thoug thought ht of of as the the data databas base e > a D0 D0 - We will use these terms interchangeably and we will only consider computer-based relational databases D0 features 4$ampes6 3 ser#er, )race, /eradata, y3, Access Sqlite, Sqlite, etc. o - Dat Data sto storage an ana agem gement ent tructure +tabes, coumns, etc. o Data integrity management o - e ecu curi rity ty mana manage geme ment nt - ut utii-us user er acce access ss cont contro ro - 0a 0ac! c!up up and and rec reco# o#er ery y mana manage geme ment nt - Databas Database e angua anguage ge and and appica appicatio tion n progra programmi mming ng inter interface faces s uery anguage +3 o - Datab Database ase comm commun unic icati ation on inte interf rface aces s Importance of D0
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a!es a!es data data manage managemen mentt more more efficie efficient nt and and effec effecti# ti#e e uery anguage anguage aows support support for data-retrie data-retrie#a, #a, data-manip data-manipuatio uation, n, structured reporting, and &uic! answers to ad hoc +non-structuredone-off &ueries - (ro#id (ro#ides es bette betterr access access to to more more and better better-ma -manag naged ed data data - Reduc Reduces es the the prob probabi abiit ity y of of inco inconsi nsiste stent nt data data - (romot (romotes es integ integra rated ted #iew #iew of of organi organisat sation ion"s "s oper operati ations ons What happens when database management is not used? - @ie @ies s u use sed d to to man manag age e ffin inan anci cia a data data - Ao data databa base se syst system ems s in in pa pace ce Rea ife e$ampes - Booge da data center - /ime /imes1a s1ast st ' Ret Retai aio ors rs"" (red (redic icti tion ons s
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Week 2 - elational Data Model elational Database -
5 gener genera a purpo purpose se D0 D0 are based based on on the rea reatio tiona na data data mode mode.. /his means that a data is stored in a number of tables +with named coumns @or historica, historica, mathematica mathematica reasons reasons such such tabes tabes are referred referred to as as relations /he ta tabes sh show data together data together with relations!i"s between relations!i"s between the data 4nabes 4nabes users users to to #iew #iew data data ogica ogicay y as two-dimens two-dimensiona iona structure structure composed composed of rows and coumns This This course course is solely solely on on relati relationa onall databas database, e, and on on relati relationa onall DBMS
elational Database Management System (DBMS) -
3oo!s i!e a coection of tabes
Reationa Database - 5 precise precise,, concept conceptua ua way way of descr describi ibing ng the the data data stored stored in a reati reationa ona database tructure of the data o )perations on the data o 1onstraints on the data o Reation +/abe - to tores res data data on indi indi#idu #idua a thing things, s, which which are cons conside idered red impo importa rtant nt (eope +4mpoyee, tudent, taff ember o )b9ects +0oo!, (roduct, 3ecture Room o 1oncepts 5ctions +/ransaction +/ransaction in an 5/, 0orrowing a boo! from the o ibrary tructure of the data ' Reation +/abe - 5 rea reati tion on con consis sists ts of of rows rows and and co coum umns ns - /he /he co coum umn hea heade derr wi wi describe the describe the data - /he number number of cou coumns mns are fi$ed fi$ed - defini definite te number number - /he number number of rows rows are are not not ffi$e i$ed d ' indef indefini inite te numb number er - 4ach 4ach inters intersect ection ion betw between een a row row and and coumn coumn +ce +ce conta contains ins a single item of data - 4ach 4ach row wi wi des descr crib ibe e a single instance of instance of the data 4$ampe Reation - 0oo!
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4ach row shoud describe a singe boo! using the coumn headers /his ma!es each row a record pro#iding pro#iding information about a singe boo! o - tudent +possibe coumns header for storing s toring a student"s identity information o 4$ercise o
/upe /upe +Row + Row - 5 re reat atio ion n con consis sists ts of of tup tupe es s +Row +Rows s - 5 ttup upe e is an orde orders rs ist ist of #au #aues es - /upes /upes are usua usuay y written written in in parenthe parentheses, ses, with with commas commas separa separating ting the #aues +or components 4$ampe6 4mpoyee Reation +C<E, I/%, , /echnician /echnician o - )rde )rderr is sign signif ific ican antt 4$ampe6 the tupe +C<E, /echnician, /echnician, I/%, , is different from the o tupe abo#e 5ttribute +1oumn@ied - In order order to to be abe abe to refer to the the different different components components in a tupe, tupe, we wi wi assign them names +caed attributes 4$ampe6 @or the tupe +C<E, I/%, ae, /echnician, /echnician, we might o choose the attributes ID, Aame, Bender, and and FobDescription Data /ype - /he #au #aue e of an attrib attribute ute beo beongs ngs to to a domai domainG nG aso aso !nown !nown as a data ty"e of an attribute - 5 attribu attributes tes must must ha#e ha#e a data data type, type, but but the the data data types types a#aiab a#aiabe e depend depend on the particuar D0 - 1ommon 1ommony y a#aia a#aiabe be data data type type among among diffe differen rentt impeme impementa ntatio tions ns /4H/ for te$t strings o IA/4B4R for integers o R453 for rea numbers o D5/4 for dates o chema - In the the reatio reationa na data data mode mode, , a reat reation ion is is often often descri described bed usin using g a sc!ema which consists of
Infosys 222 /he names of the reation /he set of its attributes +sometimes with data types o - 4$ampe6 /he reation 4mpoyee can be described by the schema 4mpoyee +ID, Aame, Bender, FobDescription o 4mpoyee+ID IAB4B4R, Aame /4H/, Bender /4H/, FobDescription /4H/ o - /he schemas of a reations in a database form a database sc!ema Reation Instance - 5 reation is not staticG it changes o#er time Inserting new tupes o pdating components of e$isting tupes o Deeting tupes o - 5 set of tupes for a reation at a moment is an instance of that reation - 5 D0 maintains ' the current instance 8ey - 5n attribute or a set of attributes used to uni&uey identify a tupe /wo empoyees wi not ha#e the same ID o - /his uni&ue attribute attributes is caed the #rimary $ey - =ou can introduce an artificia !ey, if no suitabe attributeattributes e$ist o
Wee! 2 ' 4RD (art J Database Design ' 4ntity Reationship Diagrams Database Design - 1reate a bueprint - Aeed to consider What tabes, attributes and !eys needed? o What is the database going to be used for? o - 1onceptua design 0uid a mode independent of the choice of D0 o - 3ogica 1reate the database in a gi#en D0 o - (hysica design %ow the database is stored in hardware o 4ntity Reationship +4R mode
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/he concept is originay defined by 1hen +JEC, which has been adopted and refined by practitioners as the eading method to carry out database design - 5n 4R mode is a systematic way of describing and defining a business process. /he process is modeed as entity sets that are in!ed with each other by reationships that e$press the dependencies and re&uirements between them - 5n 4R diagram +4RD is used as a too for 4R modeing, which aso pro#ides a representation of the 4R mode 4R odeing and the Reationa Data ode - 4ntity set -K reation - 5ttributes -K attributes - Reationships -K /he connections between the reations 4ntityReationship odeing - 4R odeing is used for conceptua design 4ntity et6 ob9ects or items of interest o 5ttributes6 facts about, or properties of, an entity. /hey describe an entity o Reationships6 in!s between entities o 4ntity et 4ntities - 4ntity set represents ob9ect or things of interest - 5 genera type (hysica things i!e students, ecturers, empoyees, products o ore abstract things i!e transactions, orders, courses, pro9ects o - Instances of that particuar type, are entities - 5n entity set shoud be named with a singuar noun Reated to business characteristics, meaningfu and sef-documenting o ni&ue and concise, readabe o
- 4ntity et -K Reation /abe - 4ntity -K Row /upe Record 4ntity ' 5ttributes beonging to it
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5ttributes are facts, aspects, properties, or detais about an entity i.e. students ha#e IDs, names, courses, addresses, L. o
Infosys 222 - )ne or more attributes define the !ey 5ttributes - 1haracteristics of entities - Domain is set of possibe #aues +defined by ‘data type" - Represented as coumns in a database - Design note Aame descripti#ey and meaningfuy o Aaming con#ention ' came casing +the first etter of the first word is o owercase, but subse&uent first etters are uppercase
/ypes of 5ttributes 1% #rimary $ey 2% Sim"le (Single-&alued) 1annot be subdi#ided o Bender, marita status '% om"osite Is composed of se#era component parts o 5ddress6 streetAumber, surburb, city, *ip code Aame6 firstAame, astAame o model ' )perationa decision ' reduce redundancy and o inconsistencies, ease of retrie#a, usage 1reate additiona attributes for an entity ' #iabe option 1reate an entirey new entity ' Aeeds Reationships ' /01 *% Multi-&alued utipe #aues possibe o ustomer entity with a "!one attribute o home(hone office(hone +acultyMember with a quali+ication attribute o ‘0c" ‘c" ‘(hD"
Infosys 222 o model ' )perationa decision ' reduce redundancy and inconsistencies, ease of retrie#a, usage 1reate additiona attributes for an entity ' not the best option 1reate an entirey new entity ' Aeeds Reationships ' /01 ,% Deri&ed - Vaues that are cacuated from other attributes 5ge6 cacuated from date)f0irth o )rdertota -K cacuated from unit(rice $ &uantity o - /o mode Aormay not stored o )perationa decision ' resource use, usage of data o Decisions ' %ow to mode attributes - %ow woud the data be used - /a!e future growth into consideration - )perationa efficiency 4iminate inconsistencies o Reduce redundancy o o
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(rimary 8ey - /he primary !ey is an attribute or a set of attributes that uni&uey identify a specific instance of an entity - 4#ery entity in the data mode must ha#e a primary !ey whose #aues uni&uey identify instances of the entity - /o &uaify as a primary !ey for an entity It must ha#e a non-nu #aue for each instances of the entity o /he #aue must be uni&ue for each instance of an entity o /he #aues must not change or become nu during the ife of each entity o instance 1andidate 8ey - In some instances, an entity wi ha#e more than one attribute that can ser#e as a primary !ey - 5ny !ey or minimum set of !eys that coud be a primary !ey us caed a candidate !ey - )nce candidate !eys are identified, choose one, and ony one, primary !ey for each entity - 1andidate !eys which are not chosen as the primary !ey are !nown as aternate !eys - If none of the candidate !eys are suitabe ' introduce - 4$ampe (ubisher 4ntity ' @rom the case description o (ubisher Aame (ubisher (hone number May change over time 5uthor 4ntity ' @rom the case description o 5uthor Aame
Infosys 222 May not be unique / May change over time 0oo! 4ntity ' @orm the case description o I0A number ' unique, no change over time, not null /ite /he 4ntities and 5ttributes
Reationships - Reationships are an association between two or more entities ase description o 0oos can be ritten by one or more authors o 5uthors can aso rite more than one boo! o (ubishers "ublis! many boo!s o )ne boo! is "ublis!ed by one pubisher o - Reationships ha#e 5 name ' #erb o 5 set of entities that participate in them o )perate in both directions o 5 cardinaity ratio o 5 degree ' the number of entity sets that participate +most ha#e degree o 2
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1ardinaity Ratios - 4ach entity in a reationship can participate in *ero, one, or more than one instances of that reationship - /his eds to < types of reationship - utipicity )ne to many +J6 o any to many +6 o )ne to one +J6J o - )ptionaity )ptiona or mandatory o )ne /o any Reationship
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Indicates that a singe occurrence of one entity is associated with one or more occurrences of the reated entity 0J-K(J o (J-K0J, 02 o 5 boo! must ha#e a pubisher o /he store may not be currenty ha#ing any boo!s pubished by pM o - /o create (ace primary !ey of parent as @oreign !ey of chid o 1ardinaity ' utipicity and )ptionaity
@oreign 8ey
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5 foreign !ey is way for na#igating between different instances of an entity 5ppears on the many side of a J6
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any /o any Reationship
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5n entity of either set can be connected to many entities of the other set 0J -K 5J, 5< o 5J -K 0J, 02, 0< o In the initia mode
In the data ' 0oo!
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In the data ' 5uthor
Remo#ing 6 Reationships - any to many reationships are diffeicut to represent - We can spit a many to many reationship into twon one to many reationships - /he new entity ' 5ssociati#e entity represents the 6 reationship - 5n associati#e entity set is used to represent a reationship which often has its own attributes that do not beong to other entity sets Reso#e ' In the mode
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In the data ' 0oo!5uthor
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(rimary !ey? ometimes more than one attribute is re&uired to uni&uey identify an entity 5 primary !ey is made up of more than one attribute is !nown as a composite !ey
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)ne to )ne Reationship
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4ach entity of either entity set is reated to at most one entity of the other set 4J -K 5J o 42 -K 5< o 4< -K 5: o - 5n author has one and ony one address - 5ddress -K attribute of empoyee 5ttribute #s 4ntity - If we ha#e se#era addresses per 5uthor, +%ome 5ddress and tudio 5ddress 5ddress must be an entity ' attributes cannot be muti #aued o
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4ntities and 5ttributes - ometimes it is hard to te if something shoud be an entity or an attribute /hey both represent ob9ects or facts about the word o /hey are both often represented by nouns in descriptions o - Benera guideines 4ntities can ha#e attributes but attributes ha#e no smaer parts o 4ntities can ha#e reationships between them, but an attribute beongs to o a singe entity a!ing 4R odes - /o ma!e an 4R mode you need to identify from the description 4ntities o 5ttributes o Reationships o 1ardinaity ratios o - Benera guideines ince entities are things or ob9ects they are often nouns in the description o 5ttributes are facts or properties, and so are often nouns aso o Verbs often describe reationships between entities o
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Reading - 4R modeing with crow"s foot notation ummary ' you shoud - 0e abe to arri#e at a ogica 4R mode based on a case description - Aow about some !ey 4RD concepts6 entities, attributes, !eys and reationships
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Degree of a reationship - Is the number of entity sets that participate in a reationship - /he three common reationship degrees J. nary +degree J 2. 0inary +degree 2 <. /ernary +degree < - "igher degree relationships are possible but rarely encountered in practice 0inary Reationships - 0etween the instances of two entity sets - /he most common type of reationship encountered in data modeing
nary Reationship - 0etween the instances of a singe entity set +recursi#e reationships - 1ardinaity coud be J6J, J6 or 6A
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o o o
4.g. each person is married to 9ust one person -K J6J ode as an attribute within the same entity Don"t draw
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1ardinaity coud be J6 4.g. 4ach empoyee can manage many other empoyees or no one but o each empoyee is managed by ony one other empoyee or not managed by any one at a
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1ardinaity coud be 6A 4.g. 1ourse - IA@)=222 o (rere&uisite6 IA@)=JJN or J2N, or 1)(1I JNO or JNC 1ourses - IA@)=<
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/ernary Reationships - imutaneous reationship among the instances of < entity sets - 4.g. 4mpoyees with many re&uired s!is can be assigned to many pro9ects )ne empoyee has many s!is and is assigned to many pro9ects o )ne pro9ect incudeds many empoyees with many re&uired s!is o )ne s!i can be possessed by many 4mpoyees wor!ing in many pro9ects o /%R44 GA reationships o
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It is recommened that a ternary +or higher reationships are con#erted into associat#e entities Represent the ternary reationship with an associati#e entity and three binary reationships
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urrogate 8eys - 1an be substitute singe #aue surrogate !eys for arge composite !eys
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Aote6 the reationship changes to non-identifying
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Wea! 4ntity - 5n entity is considered wea! if the e$istence +of an instance of that entity depends on the e$istence +of an instance of another entity - 5 wea! entity can be identified uni&uey ony by considering the primary !ey of another +owner entity
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)wner entity set and wea! entity set must participate in a one-to-many reationship set +one owner, many wea! entities
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/he (8 of the ‘parent" entity must be part of the (8 of the wea! Wea! entities are otherwise 9ust i!e reguar entities +name, (8s, @8s, attributes, reated to other entities, etc. - /he reationship between a strong entity set and a wea! entity set is caed an identifying supporting reationship Identifying and Aon Identifying Reationship - Identifying 5 chid ob9ect +wea! entity set cannot e$ist without the parent ob9ect o and chid ob9ect cannot be uni&uey identified without the parent If the parent entity is deeted, then the chid entity must be deeted o Identifying reationships e$ist when the primary !ey of the parent entity o is incuded in the primary !ey of the chid entity
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Aon Identifying 5 non- identifying reationship means that a chid entity is reated to o parent entity but it can be identified independenty of the parent entity /he chid item shoud be !ept e#en though the parent is deeted o
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5 non-identifying reationship is when the primary !ey attributes of the parent entity must not become primary !ey attributes of the chid entity
Benerai*ation - (rocess of defining genera entity types from a set of speciaised entity types by identifying their common characteristics
uperset and ubset - /he entity %oury4mpoyee is incuded in the entity set 4mpoyee 5 entities of one are aso entities of another o - %oury4mpoyee is the subset +or subtype subcass - 4mpoyee is the superset +or supertype supercass - ub-types +instances may be mutuay incusi#e or e$cusi#e
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uperset6 a generic entity set that has a J6J reationship with one or more subsets
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ubset6 a subgrouping of the entities in an entity set that has distinct attributes Incusi#e +)#erap - Define whether it is possibe for an instance of a supercass to simutaneousy be a member of one or more subcasses - 5 supercass instance can o#erap more than one subcass 5 person can be both a student and staff o
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4$cusi#e +Dis9oint - tates that if an instance of a superset is a member of any subset, then it cannot be a member of more than one subset 5 student is either a Braduate or (ostBraduate, not both o o
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Discriminators - 5 discriminator is an +optina attribute that determines which subtype is appropriate - 4$ampe6 /he attribute PisBradtudent,Q which appears in /D4A/ on the prior side is a discriminator Wi ha#e a domain of P=esQ and PAoQ o uperset and ubset ' Identifiers and Inheritance - /he identifier of the super type and a of its subtypes must be identica - /he identifier of the super type becomes the identifier of the reated subtype+s - Rename if re&uired - Inheritance means that the entities in the subtypes PinheritQ the attributes of the supertype entity cass - 4$ampe6 Braduate inherits the attributes of (erson and tudent
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Design (rincipes for Data odeing - /here are no right or wrong data mode. Bood data modeing is difficut - sefu design principes 0e faithfu to the specification of the re&uirement o se common sense and ma!e assumption ony if the specification fais to o e$pain 5#oid dupication and other redundant information o
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Reading6 http6www.inf.unib*.itfranconiteaching2NNNct:;Jer-modeing =ou shoud be abe to - 5rri#e at a ogica 4R mode based on a case description - 5ppy the 4RD concepts to a database design tas! Database Fourney - 1onceptua ode 4ntity, 5ttributes, Reationship +J to , to and J to J o
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3ogica ode (8, @8, 5ssociati#e 4ntity, Wea! and trong 4ntity, o Benerai*ationpeciai*ation +4$cusi#e and Incusi#e, nary Reationship L. - (hysica ode /abe, 1oumn, Data o
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Aormaisation - 5 process of organi*ing the fieds and tabes of a reationa database to minimi*e redundancy and dependency - It is a theoretica techni&ue to refine and impro#e +or e#en to begin the ogica data modeing - /he idea is that an entity set +tabe shoud be about a specific topic and that ony those attributes +coumns which support that topic are incuded
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Data Dupication - Increases storage and decreases performance
Data odification Issues J. Insert 5nomay
2. pdate 5nomay
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<. Deete 5nomay
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In summary - %a#ing one entity that ser#es many purpses introduces many chaenges Data Dupication o Data pdate Issues o - Aeed Aormaisation /o minimi*e dupicate data o /o minimi*e or a#oid data modification issues o teps of Aormai*ation - @irst Aorma @orm +JA@ /o remo#e a muti#aued attributes and to define a primary !ey for a o gi#en data structure - econd Aorma @orm +2A@ /o remo#e a paria functiona dependedcies that e$ist between a non-!ey o attribute and part of a primary !ey for a gi#en data structure with a composite !ey - /hird Aorma @orm +
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@irst Aorma @orm +JA@ - /here shoud be a singe fact in each row - 5 the primary !ey attributes are defined - 5 attributes are +unctionally de"endent on the primary !ey +in part or in whoe JA@ teps J. n Aormai*ed form
2. @ind a good (8 @ind the repeating group o
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<. a!e the obi#ous identifier of the set and the identifier of the repeating froup a composite primary !ey )bi#ous identifier ' )rder ID o Identifier of the repeating group ' (roduct ID o (rimary 8ey ' )rder ID, (roduct ID o JA@ )rder+orderID, orderDate, customerID, customerAame, customer5ddress, productID, productDesc, product@inish, unit(rice, ordereduantity econd Aorma @orm +2A@ - Remo#e a #artial .uncional dependencies @unctiona Dependencies - We say an attribute, 0, has a functiona dependency on antoher attribute, 5, if for any two records, which ha#e the same #aue for 5, then the #aues for 0 in these two records must be the same - We iustriate this as6 5 -K 0
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(artia Dependency - When an attribute 0 is functinay dependent on an attribute 5, and 5 is a component of a mutipart candidate !ey
econd Aorma @orm +2A@ - JA@ )rder+orderID, orderDate, customerID, customerAame, customer5ddress, productID, productDesc, product@inish, unit(rice, ordereduantity J. 4$amine a non !ey attributes 2. Remo#e a (artia @unctiona dependencies to separate reations <. If any attributes are functionay dependent on the compete composite !ey, incude them in a separate reation, indicating foreign !eys
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/hird Aorma @orm +
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We say that 1 is transit#ey depednet on 5 through 0
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Aotes on Aormai*ation - If the gi#en data structure in JA@ has a singe attribute primary !ey, then there is no partia functiona dependencies and hence the JA@ is in 2A@ - If the gi#en data structure in 2A@ has no transiti#e functiona dependencies then it is in
Infosys 222 It is not uncommon to re#erse the process of normaisation to induce redundancy and eiminate the number of eneity sets for the purpose of performane and maintenance of the database #ote$ all these considerations must not be ta!en lightly without reasoning and weighting between bene%its and costs
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