Joining data

Joining data追加的字段来自一个或多个表。ArcGIS提供加入数据的几种方法，这取决于数据的来源和数据的基数。本主题介绍了可用的选项，以及如何决定哪个选项是最好的应用程序。

// Create the query definition.
IQueryDef queryDef = featureWorkspace.CreateQueryDef();// Provide a list of tables to join.
queryDef.Tables = "streets, altname";// Set the subfields and the WhereClause (in this case, the join condition).
queryDef.SubFields = "streets.NAME, streets.TYPE, altname.ST_NAME, altname.ST_TYPE";
queryDef.WhereClause = "streets.OBJECTID = altname.JOINID";// Get a cursor of the results and find the indexes of the fields to display.
using (ComReleaser comReleaser = new ComReleaser())
{ ICursor cursor = queryDef.Evaluate();comReleaser.ManageLifetime(cursor);int streetsNameIndex = cursor.FindField("streets.NAME");int streetsTypeIndex = cursor.FindField("streets.TYPE");int altnameNameIndex = cursor.FindField("altname.ST_NAME");int altnameTypeIndex = cursor.FindField("altname.ST_TYPE");// Use the cursor to step through the results, displaying the names and altnames of each // street.IRow row = null;while ((row = cursor.NextRow()) != null){Console.WriteLine("Street name: {0} {1}. - Alt. name: {2} {3}.", row.get_Value(streetsNameIndex),row.get_Value(streetsTypeIndex), row.get_Value(altnameNameIndex), row.get_Value(altnameTypeIndex));}
}

// Make the new TableQueryName.
IQueryName2 queryName2 = (IQueryName2)new TableQueryNameClass();
queryName2.QueryDef = queryDef;
queryName2.PrimaryKey = "streets.StreetID";
queryName2.CopyLocally = true;// Set the workspace and name of the new QueryTable.
IDatasetName datasetName = (IDatasetName)queryName2;
datasetName.WorkspaceName = workspaceName;
datasetName.Name = "StreetsJoin";// Open the virtual table.
IName name = (IName)queryName2;
ITable table = (ITable)name.Open();

// Build a memory relationship class.
Type memRelClassFactoryType = Type.GetTypeFromProgID("esriGeodatabase.MemoryRelationshipClassFactory");
IMemoryRelationshipClassFactory memRelClassFactory = (IMemoryRelationshipClassFactory)Activator.CreateInstance(memRelClassFactoryType);
IRelationshipClass relationshipClass = memRelClassFactory.Open("ParcelsOwners", parcelsFeatureClass,"PARCEL_ID", (IObjectClass)ownersTable, "PARCEL_ID", "Is Owned By", "Owns", esriRelCardinality.esriRelCardinalityOneToOne);// Open the RelQueryTable as a feature class.
Type rqtFactoryType = Type.GetTypeFromProgID("esriGeodatabase.RelQueryTableFactory");
IRelQueryTableFactory rqtFactory = (IRelQueryTableFactory)Activator.CreateInstance(rqtFactoryType);
ITable relQueryTable = (ITable)rqtFactory.Open(relationshipClass, false, null, null, String.Empty, false, false);

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