GIS520DataCardinality

DataCardinality

Outline

TableAssociations Datacardinality MethodsforcreatingrelationshipsinArcGIS

TableAssociations

Establishingassociationsbetweentableswillallowaccessingdatainallrelatedtables.

AssociationsinArcGIS canbeestablishedbetweenmultipledataformats:suchasshapefiles,ArcInfo tables,featureclassesinpersonalgeodatabase,ortablesinanArcSDE enterprisegeodatabase.

Establishingassociationsbetweenalayer(spatialcontext)andatable(additionalattributes)willallow:

a)tosymbolizeorlabelfeaturesbasedonattributesfromthejoinedtableorb)toviewrecordsinacorrespondingtablewhenattributesareselectedinthe

relatedtable

Thewaytablesarerelatedtooneanotheriscalledcardinality.

DataCardinality

Therearefourcardinalitytypes:onetoonemanytooneonetomanymanytomany

Itisimportanttounderstandwhichrelationshiptype ispresentbetweenthetablestopreventpotentialrecordemissionerror.

FormoreinformationonthebasicsofRelationshipsandArcGIS,viewArcGISResourceCenteronline

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Relationships_and_ArcGIS/004t00000001000000/

MethodsforcreatingrelationshipsinArcGIS

InArcMaprelationshipscanbecreatedbyjoining orrelating tablestogether

UseJoin:foronetoone ormanytoone relationshipbetweenalayerandatable

Database Example: one-to-one relationship from a database where the unique identifier of Product ID is used to join two tables

MethodsforcreatingrelationshipsinArcGIS

InArcMap relationshipscanbecreatedbyjoining orrelating tablestogether.

Userelate:ifthereisaonetomany oramanytomany relationshipbetweenalayerandatable.

EPA: Example one-to-many relationship: Coordinator is assigned one Region, which spans many States

MethodsforcreatingrelationshipsinArcGIS

Differencesbetweenjoinandrelate:

Join: Allcolumnsfrombothtablesareappendedtogether intoonelargetable. Itwillallowtosymbolizeorlabelfeaturesbasedonattributesfromthejointable. Permitsonlyonetoone ormanytoone cardinality. Incorrectcardinalityresultsinomittedrecords.

Relate: Temporaryassociationisestablishedbetweenthetables,whichissavedinanArcMapdocument. Therelatedtablesareviewedseparately. Itwillnotallowtosymbolizeorlabelfeaturesbasedonattributesfromtherelatetable. Canbecreatedbetweentablesofallcardinalitytypes. Canbecreatedregardlessofthecardinalitybetweentableswithoutthedangerofomittinginformation.

MethodsforcreatingrelationshipsinArcGIS

Thebasicsofcreatingrelationshipsbetweentablesinclude:

Findingthecommoninformationbetweenthetables Understandinghowvaluesineachjoincolumnmatch

Inordertoassociatetables:

Commoninformationhastoexistinbothtablessuchas:countyname,zipcode,buildingID,parcelID,etc.

Commoninformationhastobestoredasthesamedatatypeineachtable

ThenamesofthecolumnstoberelateddonothavetobethesameThedatatypeandvalues inbothcolumnsmustbethesame