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Chapter 4. Searching and Analyzing Data

Chapter 4. Searching and Analyzing Data

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TheDataViewisadata-bindableviewofaDataTablethat

presentsdatawithdifferentsortordersandfilters.Youcan

createmultipleviewsforeachtable;everytablehasadefault

dataview.TheDataViewManagerclasshelpstomanagethe

defaultdataviewsfortablesinaDataSet.Section4.5shows

howtousetheDataViewtofilterandsortdatainaDataSet.

Section4.6showshowtofilteradataviewforrowsthathave

nullvalues.

TheDataTableandDataViewclassesbothprovideseveralways

tolocaterecordsfromspecifiedcriteria.Searchinganexisting

tableorviewsavesaroundtriptothedatabaseserver.Although

theDataViewiscreatedfromaDataTable,searchingisdone

differentlyineach.Section4.4showshowtofindrowsina

DataTableandinaDataView.Section4.7showshowtoaccess

deletedrowsinDataTable.

ADO.NETdoesnotprovideawaytocomparetwoDataSet

objectswithidenticalschemastodeterminethedata

differencesbetweenthetwo.Section4.1createsamethod

GetDataSetDifference()thatreturnsthedifferencesasa

DiffGram,whichisanXMLformatthatidentifiesoriginaland

currentversionsofdataandisusedby.NETtoserializeand

persisttheDataSet.

InadditiontorecipesabouttheDataRelation,DataSet,

DataTable,andDataViewclasses,thischaptercoverstopics

including:

ADO.NETdoesnotprovideawaytogettheTOPNrows

fromaDataTablebasedonthevalueofacolumninthe

table.Section4.8showshowtobuildafilteronthe

DataViewatruntimetoreturntheTOPNrows.

Queriessometimesneedtobebasedondatafrommore

thanonedatasource.Section4.2showshowtoreturna

resultsetfromaquerybasedonmorethanonetableusing



adhocconnectornamesthatallowdatafrom

heterogeneousdatasourcestobeaccessedbyproviding

theconnectioninformationintheSQLstatement.

TheCOMPUTEBYclausereturnsbothsummaryanddetail

datainasingleresultsetfromasingleSELECTstatement.

Section4.9showshowtoexecuteaCOMPUTEBYstatement

andhowtonavigatetheresultset.

TheShapelanguageusesDataShapingServicesforOLEDB

asanalternativetoJOINandGROUPBYsyntaxtogenerate

hierarchicalresultsets.Section4.10showshowtousethe

ShapelanguagetogetahierarchicalresultsetfromSQL

ServerusingtheOLEDB.NETdataprovider,andhowto

navigatetheresultset.

ExecutingCommonTableExpression(CTE)andrecursive

queriesandworkingwiththereturnedresultsetsis

demonstratedanddiscussedinRecipesSection4.12and

Section4.13.

Retrievingrandomsamplesofdata,retrievingrankedresult

sets,workingwithpivottables,andinvokingfunctionsforeach

rowinaresultsetarealsothetopicsofrecipesinthischapter.



Chapter4.SearchingandAnalyzingData

Introduction

DeterminingtheDifferencesinDataBetweenTwoDataSet

Objects

CombiningDatafromHeterogeneousDataSources

FilteringRowsinaDataTableorDataView

FindingRowsinaDataTableorDataView

FilteringandSortingDatainaDataTable

FilteringNullFieldValuesinaDataTable

AccessingDeletedRowsinaDataTable

SelectingtheTopNRowsinaDataTable

ExecutingQueriesThatUseCOMPUTEBY

UsingtheShapeLanguagetoRetrieveHierarchicalData

RetrievingaRandomSampleofRecords

UsingaCommonTableExpression(CTE)

ExecutingaRecursiveQuery

RetrievingaRankedResultSet

RetrievingaPivotandUnpivotTable

InvokingaFunctionforEachRowinaResultSet



Recipe4.0.Introduction

Thischapterfocusesonsearchingforrecordsinviewsand

tables,calculatingvaluesbasedonvaluesinthoseorother

tables,andnavigatingdatarelationsbetweentables.



TheDataViewisadata-bindableviewofaDataTablethat

presentsdatawithdifferentsortordersandfilters.Youcan

createmultipleviewsforeachtable;everytablehasadefault

dataview.TheDataViewManagerclasshelpstomanagethe

defaultdataviewsfortablesinaDataSet.Section4.5shows

howtousetheDataViewtofilterandsortdatainaDataSet.

Section4.6showshowtofilteradataviewforrowsthathave

nullvalues.

TheDataTableandDataViewclassesbothprovideseveralways

tolocaterecordsfromspecifiedcriteria.Searchinganexisting

tableorviewsavesaroundtriptothedatabaseserver.Although

theDataViewiscreatedfromaDataTable,searchingisdone

differentlyineach.Section4.4showshowtofindrowsina

DataTableandinaDataView.Section4.7showshowtoaccess

deletedrowsinDataTable.

ADO.NETdoesnotprovideawaytocomparetwoDataSet

objectswithidenticalschemastodeterminethedata

differencesbetweenthetwo.Section4.1createsamethod

GetDataSetDifference()thatreturnsthedifferencesasa

DiffGram,whichisanXMLformatthatidentifiesoriginaland

currentversionsofdataandisusedby.NETtoserializeand

persisttheDataSet.

InadditiontorecipesabouttheDataRelation,DataSet,

DataTable,andDataViewclasses,thischaptercoverstopics

including:

ADO.NETdoesnotprovideawaytogettheTOPNrows

fromaDataTablebasedonthevalueofacolumninthe

table.Section4.8showshowtobuildafilteronthe

DataViewatruntimetoreturntheTOPNrows.

Queriessometimesneedtobebasedondatafrommore

thanonedatasource.Section4.2showshowtoreturna

resultsetfromaquerybasedonmorethanonetableusing



adhocconnectornamesthatallowdatafrom

heterogeneousdatasourcestobeaccessedbyproviding

theconnectioninformationintheSQLstatement.

TheCOMPUTEBYclausereturnsbothsummaryanddetail

datainasingleresultsetfromasingleSELECTstatement.

Section4.9showshowtoexecuteaCOMPUTEBYstatement

andhowtonavigatetheresultset.

TheShapelanguageusesDataShapingServicesforOLEDB

asanalternativetoJOINandGROUPBYsyntaxtogenerate

hierarchicalresultsets.Section4.10showshowtousethe

ShapelanguagetogetahierarchicalresultsetfromSQL

ServerusingtheOLEDB.NETdataprovider,andhowto

navigatetheresultset.

ExecutingCommonTableExpression(CTE)andrecursive

queriesandworkingwiththereturnedresultsetsis

demonstratedanddiscussedinRecipesSection4.12and

Section4.13.

Retrievingrandomsamplesofdata,retrievingrankedresult

sets,workingwithpivottables,andinvokingfunctionsforeach

rowinaresultsetarealsothetopicsofrecipesinthischapter.



Recipe4.1.DeterminingtheDifferences

inDataBetweenTwoDataSetObjects

4.2.1.Problem

YouhavetwoDataSetobjectswiththesameschemabut

containingdifferentdataandneedtodeterminethedifference

betweenthedatainthetwo.



4.2.2.Solution

ComparethetwoDataSetobjectswiththe

GetDataSetDifference()methodinthissolutionandreturn

thedifferencesbetweenthedataasaDiffGram.

ThesolutioncreatestwoDataSetobjectseachcontaininga

differentsubsetofrecordsfromthe

HumanResources.DepartmenttableinAdventureWorks.The

GetDataSetDifference()methodtakestwoDataSetobjects

withidenticalschemasasargumentsandreturnsaDiffGramof

thedifferencesbetweenthedatainthetwo.

TheC#codeinProgram.csintheproject

DetermineDataDifferenceDataSetsisshowninExample4-1.

Example4-1.File:Program.csfor

DetermineDataDifferenceDataSetssolution

CodeView:

usingSystem;

usingSystem.Data;

usingSystem.Data.SqlClient;

usingSystem.IO;

namespaceDetermineDataDifferenceDataSets

{

classProgram



{

staticvoidMain(string[]args)

{

stringsqlConnectString="DataSource=(local);"+

"Integratedsecurity=SSPI;InitialCatalog=Adven



//FillDataSetA

stringsqlSelectA="SELECT*FROMHumanResources.D

"WHEREDepartmentIDBETWEEN1AND5";

DataSetdsA=newDataSet();

SqlDataAdapterda=newSqlDataAdapter(sqlSelectA,

da.TableMappings.Add("Table","TableA");

da.FillSchema(dsA,SchemaType.Source);

da.Fill(dsA);

//Settheprimarykey

dsA.Tables["TableA"].PrimaryKey=

newDataColumn[]{dsA.Tables["TableA"].Columns



//FillDataSetB

stringsqlSelectB="SELECT*FROMHumanResources.D

"WHEREDepartmentIDBETWEEN4AND8";

DataSetdsB=newDataSet();

da=newSqlDataAdapter(sqlSelectB,sqlConnectStrin

da.TableMappings.Add("Table","TableB");

da.FillSchema(dsB,SchemaType.Source);

da.Fill(dsB);

//Settheprimarykey

dsB.Tables["TableB"].PrimaryKey=

newDataColumn[]{dsB.Tables["TableB"].Columns



Console.WriteLine(GetDataSetDifference(dsA,dsB));

Console.WriteLine("\nPressanykeytocontinue.");

Console.ReadKey();

}



privatestaticstringGetDataSetDifference(DataSetds1,

{

//AcceptanyeditswithintheDataSetobjects.



ds1.AcceptChanges();

ds2.AcceptChanges();

//CreateaDataSettostorethedifferences.

DataSetds=newDataSet();



DataTabledt1Copy=null;

//Iterateoverthecollectionoftablesinthefir

for(inti=0;i
{

DataTabledt1=ds1.Tables[i];

DataTabledt2=ds2.Tables[i];



//CreateacopyofthetableinthefirstData

dt1Copy=dt1.Copy();



//Iterateoverthecollectionofrowsinthe

//copyofthetablefromthefirstDataSet.

foreach(DataRowrow1indt1Copy.Rows)

{

DataRowrow2=dt2.Rows.Find(row1["Departme

if(row2==null)

{

//Deleterowsnotintable2fromtabl

row1.Delete();

}

else

{

//Modifytable1rowsthatarediffere

//table2rows.

for(intj=0;j
{

if(row2[j]==DBNull.Value)

{

//Columnintable2isnull,

//butnotnullintable1

if(row1[j]!=DBNull.Value)

row1[j]=DBNull.Value;

}



elseif(row1[j]==DBNull.Value)

{

//Columnintable1isnull,

//butnotnullintable2

row1[j]=row2[j];

}

elseif(row1[j].ToString()!=

row2[j].ToString())

{

//Neithercolumnintable1no

//table2isnull,andthe

//valuesinthecolumnsare

//different.

row1[j]=row2[j];

}

}

}

}



foreach(DataRowrow2indt2.Rows)

{

DataRowrow1=

dt1Copy.Rows.Find(row2["DepartmentID"])

if(row1==null)

{

//Insertrowsintotable1thatarein

//butnotintable1.

dt1Copy.LoadDataRow(row2.ItemArray,fal

}

}

//AddthetabletothedifferenceDataSet.

ds.Tables.Add(dt1Copy);

}



//WriteaXMLDiffGramwithcontainingthediffere

StringWritersw=newStringWriter();

ds.WriteXml(sw,XmlWriteMode.DiffGram);



returnsw.ToString();

}

}

}

























TheoutputisshowninFigure4-1.



4.2.3.Discussion

ADiffGramisanXMLformatusedtospecifyoriginaland

currentvaluesforthedataelementsinaDataSet.Itdoesnot

includeanyschemainformation.TheDiffGramisusedby.NET

Frameworkapplicationsastheserializationformatforthe

contentsofaDataSetincludingchangesmadetotheDataset.

ADiffGramisXML-based,whichmakesitplatform-and

application-independent.Itisnot,however,widelyusedor

understoodoutsideofMicrosoft.NETapplications.

TheDiffGramformatisdividedintothreesections:current,

original,anderrors.Theoriginalandcurrentdatainthe

DiffGramcanalsobeusedtoreportthedifferencesbetween

dataintwoDataSetobjects.Formoreinformationaboutthe

DiffGramXMLformat,seeSection9.4.

ThesolutioncontainsamethodGetDataSetDifference()that

takestwoDataSetobjectswiththesameschemaasarguments

andreturnsaDiffGramcontainingthedifferencesindatawhen

thesecondDataSetiscomparedtothefirst.Table4-1

describeshowthedifferencesbetweentheDataSetobjects

appearintheDiffGram.

Figure4-1.OutputforDetermineDataDifferenceDataSets

solution



Table4-1.DiffGramrepresentationofDataSet

differences

Condition



DiffGramrepresentation



Rowisthe

sameinboth

DataSet1

andDataSet

2



Rowdataappearsonlyinthecurrentdata

sectionoftheDiffGramwithouta

diffgr:haschangesattribute.(Intheexample,

rowswithDepartmentIDof4and5appear.)



Rowisin



Rowdataappearsinthecurrentdatasectionof



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