Ch. 4 Notes - Acct 322
Ch. 4 Notes - Acct 322 322
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This 13 page Class Notes was uploaded by ag28 on Wednesday September 30, 2015. The Class Notes belongs to 322 at Clemson University taught by Nancy Harp in Fall 2015. Since its upload, it has received 51 views. For similar materials see Accounting Information Systems in Accounting at Clemson University.
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Date Created: 09/30/15
E h i nal ataha m Major ssues Covered in Chapter a E p rmnee E M awhaeee I ilf f t l between mam anti Falze I mcepls if Databases I wt I ENE I EE 391 H Him I ENE e Legacy Sy tems Inga SHEEP I Relations Ea39lalmeee and The Tate I H w m a Set W lS l j j Tables ti 5th Data Relatiimal What I H w 11 Query a Emblem Emma 9 2 Databases All the elds containing data about one entity one customer form a record A set of related records all customer records form a le customer le Database a set of interrelated centrally coordinated data les that are stored with as little data redundancy as possible forms a database Consolidates records previously stored in separate les into a common pool and serves a variety of users and data processing appHca ons Developed to address the proliferation of master les How to Query a Database to retrieve stored data users query databases The user selects the tables needed to produce the desired information if more tables than necessary are selected the query may not run properly P95 examples of queries l1 n e ata lilait at htt 39l39 Hello I Emitting ai attributes of Entity 39139 Recitufd fquot F it El Related group of elds E 7 w r Jr L gym air 1 79 l E Eryn mi 39139 HIE El Related group of n seal u Evu51 EH l D iwg E1 i gt E h quotan m J F 4 39 39 l 39139 Database l39 Related group tilquot 1 J All the elds containing data about one entity one customer form a record A set of related records all customer records for a le customer le A set of interrelated centrally coordinated data les that are stored with as little data redundancy as possible forms a database I39 Fila Approach Us Data base pprach ml i39l lll gammagei Frmm hi i avail c 397 irEilfa quot iii3 Lisle Fw Hal39s Database pmacl ham at 3 it i M 39i39 ii 3 a 53941 5 jtitb uia L 7 V gf g l Flm39r39ri39i39i39 fgi FIEtil 3th 331 52 Equot fe Eis 39i Emails311 Maggiyr Eliathinly 1 7 V Edam magi ngl 3151375 F E E 15 s File Based Approach tons of different les that are used separately in each department just by those in that department each department has their own master le that only they use programmers must know the physical location and layout of records other master les will collect some of the same data but they are separate Ex customer s mailing address is needed to run all 3 processes If customer s address changes there are 3 areas where this change has to be made Database Approach data is an organizational resource that is used by and managed for the entire organization stores everything in one centralized location pulls data form same place Data is a centrally stored resource data is more consistent when it is just stored one time Advantages of atabase Systems I Eliam integraiim Fill trE Juggiant Eutiltilzliiwtl Lin EEIILEIE MEEE39EHIJIE m atriuma j39lill lifl i Data Etnarhag liriia i i ii l ir39I mill Flam i1 E Litmriag nd un39lglE uEltiTi l il users fiat quot m Hedmidmu i and Elma Enemtsmtmuiee Pf D i ba E tama th mania alum bginig39ljslljmtl irl Ll39El liLiEliE l l l39l Ll39lLIE39E reducing iI39iI39Ir1tiII Lit I39I39LIJI39LiFlll terminal LiiiEIJEE HEI39E39LE ELIE i Ehmiri tzjsnenthme i Elam is EEEHJJHFJEJ mm 11m jlnE ELEnjjl Ll39 il mugs il Cthgm can 11 tliliinl li 1112 dull 393939iPEtILIIIE EiEEJE SiL L39LJLHEi aith in EM LIEEEI IH and 39I39i39L Miran I Emmfunctimm jitt lj iii Hiiliiiil l39liE luggh tuiagrj Elam Emu 39eELJ39jiiiiuj39i tii39 a imliunul EIIEEIJHELI EIEIZIL E Luci IL nLIJri emailr L39LIEIZIIEILILIEEI 9 J Data Integration master les are combined into large pools of data that many application programs access ex employee database that consolidates payroll personnel and job skills master les Data Sharing integrated data are more easily shared with authorized users Databases are easily browsed to research a problem or get detailed information underlying a report Minimal Data Redundancy amp Data Inconsistencies because data items are usually stored only once data redundancy and data inconsistencies are minimized main advantage of database systems Data Independence because data and the programs that use them are independent of each other each can be changed without changing the other This facilitates programming and simpli es data management CrossFunctional Analysis in a database system relationships can be explicitly de ned and used in the preparation of management reports a Key Te F IJT IE in Data base Systems I Datalhase management system D315 Interfam leetaateen a ft39e e appheatiens and the data in les league J HadWILL Database system Tier atahasei the Dish13 and applieatien it a l h pf g l t that aeeess the slate make 111 the quot quot 39 1 database system Database aimieistrateat D tj 39 Perseus sespmtisihle the maintaining the daEhase I Data micnary 3 Intermatien aleeat the simuetm39e atquot the database EeeIIEahle 41 m39 p353 ah example 9 a Database Management System DBMS is the program that manages and controls the data and the interfaces between the data and the application of programs that use the data stored in the database pulls the data Database System the database the DBMS and the application programs that access the database through the DBMS Database Administrator DBA responsible for coordinating controlling and managing the database someone in IT Data Dictionary contains information about the structure of the database For each data element stored in the database there is a record in the dictionary describing it The DBMS maintains the data dictionary whose inputs include new or deleted data elements and changes in data element names descriptions or uses outputs include reports that are used for system documentation database design and implementation and as part of the audit trail structure of data base eld length eld type date characters numeric which users have access to this data source of data P89 states data element name description records that it is used source eld length eld type numericalpha programs used outputs its used in authorized users other data names If quotH Physical li39e lii we Legieal Vew I Flt rsii al yil w39IIL Exactly Emer 7 the data is physically arranged and quotL H t Exactly where data ie plilreicelif stared en Lite eemputer I iiiIIii i5 i j m i i lllfz i il laymanme HE lIFH PEEKIi liarri es Cpl 9 J39 39i l39 Lair i al f i w haw peepie a ia E I if its by E D li ll 39m d date film1 1 need 111 i quot let lee Em lj where and rm the date is emuquoted ee ewemember i 9 J Database Management System DBMS allows us to know data with a logical view We know conceptually how to store data don t need to know where it is physically stored in the system People s logical views can be different depending on their function in the company Record Layout a document that shows the items stored in a le including the order and length of the data elds and the type of data stored in an accounts receivable le Database Approach provides 2 views of the data 1 Logical View how people conceptually organize and understand the relationships among data items ex sales manager views all customer information as being stored in a table 2 Physical View the way data are physically stored and arranged in the computer system DBMS software links the way data are physically stored with each user s logical view of the data allows users to access query or update the database without reference to how or where data are physically stored DBA can change physical storage to improve system performance without affecting users or application programs F quota relatiena atalaase i Meat ew EMEa ailquote relaiietaal elatalaaaea El Relatljeeal data leelel represents the eeateeptual and external llevel aehemae ae Elfelata are eta eeel iirl ta39lalea E Table it Each mm a tugll1 mutatian late ailment Keane Enemaze leafan entity Thar equivalent flu a IMFLi I39 Each cuiumn cantaina aiate alzicmt tame attribute eLE an entity Thir E3 seeluiu39ueer u a uid IrmaAlana quot THEMEJ 1 E J I 7 a n a r i u n iln HUF39 U unmet L In ImArili a quotI PllJ lI i NJ i n J a El jjJm HM lmlquot Relational Databases how you link information together DBMS is characterized by the logical data model or abstract representation of database content Relational data model represents conceptual and externallevel schemas as if data are stored in 2D tables Tuple each row in a table contains data about a speci c item in a database table ex each tupe contains data about a particular inventory item that SampS carries Each column contains data about an attribute of that entity ex each column contains data about speci c inventory attributes like color price a quotH H l ti l ata EEEE Typea f A FiUUTEEi I Primary lie Pie attribute er eerribe elf attributea iibat U iq ueljJ itieuti ea a be eeiiie iii a table I Fereiga lief u attribute wbieb ia a i Frir arjv key iii auetber table and ia uaeti te be tables E e Primary Key the database attribute or a combination of attributes that uniquely identi es a speci c row in a table tes what you are dealing with ex in customer table it will be customer number usually a single attribute ex primary key is Item as it uniquely identi es each merchandise item that SampS ses Foreign Key an attribute in a table that is also a primary key in another table and is used to link the two tables Ex customer is the primary key in the Customer Table and a foreign key in the Sales Table In the Sales Table Customer links a sale to data about the customer who made the purchase as contained in the Customer Table Desugning a Relatinal Database EEI39EL Req tremmits Fm Rela mal s l Eta I vellum must the l vellum Primary 12ch must mis t data mill Fm e gn mast main u same tissues u Primary he in madam It All i h f Bi39L E iEI EEE must identify a chatamer Inf u HIE idm ed the Ember El iguana If demise is not designed Fmper r data errors can MEN 1 Mama tn misting this an 11 mn mllfmmirrIHL I Eue tn mmljple mvl l im a EMIWE l mat umelf Umblu in add I rumn39l 1n 1 J39E 39d ih 1 Delete nnmaly Hamming i rmrr alen ra39nm39 svumh amlud it 2 KNOW details for exam Effects of Ways of Storing Information 1 Store all data in one uniform table Con 1 stores a lot of redundant data le maintenance unnecessarily timeconsuming and errorprone Con 2 problems occur when invoice data are stored in these types of tables update insert and delete anomaly Update Anomaly occurs because data values are not correctly updated ex changing a customer s address involves searching the entire table and changing every occurrence of that customer s address Overlooking even one row creates an inconsistency because multiple addresses would exist for the same customer Insert Anomaly occurs because there is no way to store information about prospective customers until they make a purchase ex if prospective customer data is entered before a purchase is made the Sales Invoice column would be blank but since Sales Invoice is the primary key in this case it cannot be blank Occurs because of way data is stored you re unable to enter a new record Sale has to be triggered before you can enter invoice cannot enter data into system the way you would like to Delete Anomaly occurs when deleting a row has unintended consequences ex if customer addresses are stored in the Sales table then deleting the row where the only sale to a customer is stored results in the loss of all information for that customer You want to delete something but because of way chosen to store it you unintentionally delete something else 2 Vary the number of columns reduces data redundancy and eliminates some anomalies but company now has to decide in advance how many item numbers to leave room for in each row 3 A set of tables THE SOLUTION all these issues are solved using a relational database Design Requirements for wellstructured normalized Relational Database 1 Ever column in a row must be single valued only one value per cell 2 Entity integrity rule Primary keys cannot be null a primary key cannot uniquely identify a row in a table if it is blank A nonnull primary key ensures that every row in a table can be equaHy idenU ed 3 Referential integrity rule Foreign keys if not null must have values that correspond to the value of a primary key in another table for references to worklink up the data has to be equal in both tables ensures database consistency that the link will work primary and foreign key have to be same piece of data foreign keys can contain null values 4 All nonkey attributes in a table must describe a characteristic of the object identi ed by the primary key other info in table needs to relate back to the primary key 9 esign I ng a Re I atienal Data base Jaymeaches tn a Hele unel etehee 1 H l e r 39 tg lie l huge table it Th t use rules if demmp se table imp in set fiall l We sure lieu integrate the tables prmf f mign heir quotmieg ti e The eeemp ee alleles are what is Emma as Fur mquot at EMF and titty are Iiree i ete ert and delete enemies 2 Element i d i g can Use lmtmledge if business Pm and info needle lit Efr l a whet gees in a er Use that a set EFF relational tables that start out as EMF J 2 Approaches to Database Design Normalization begins by assuming that everything is initially stored in one large table Rules are then followed to decompose that initial table into a set of tables in what is called third normal formquot 3NF because they are free of update insert and delete anomalies if you achieve it database will be free of those anomalies starts with all data together Semantic Data Modeling designed uses knowledge of business processes and information needs to create a diagram that shows what to include in a fully normalized database This diagram is used to create a set of relational tables that are already in 3NF Instead of starting with everything in one giant table you use excel knowledge to factor out data needed and table it belongs in start out with separated data
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