ArcEngine查詢統計IQueryFilter、ISpatialFilter、IQueryDef 、WHEREclauses

用ArcEngine的接口做過查詢統計的同學應該知道，由於ArcEngine並沒有完整支持SQL，所以做簡單的查詢還好，稍微複雜一點就開始捉襟見肘了。
現在總結一下幾種查詢的方法：
1.IQueryFilter、ISpatialFilter接口。
這是最常見的，把參數設置進去，然後調用IFeatureClass或者ITable的Search方法就行。可以轉爲IQueryFilterDefinition接口設置Order By和Group By語句。
2.IQueryDef接口。
個人覺得這個接口最方便，可以設置多表查詢。雖然有些幫助文檔說不能使用Order By和Group By語句，但是其實是可以的，比如可以這樣設置：
queryDef.Tables = “tableA Group by Field01”;
queryDef.SubFields = “Field01”;
或者
queryDef.Tables = “tableA”;
queryDef.SubFields = “Field01, COUNT(Field01)”;
queryDef.WhereClause = “Field01 is not null GROUP BY Field01 HAVING COUNT(Field01) > 1”;
但是這個接口只可以用在GeoDatabase，不能用於ShapeFile和Coverage數據。
3.使用IDataStatistics接口，然後調用Statistics方法返回IStatisticsResults對象，可以獲取六種統計結果。
4.另外還要加一種方法，就是IWorkspace.ExecuteSQL，可以直接輸入SQL語句，但是這個方法沒有返回值，不能獲取結果，所以只有在做一些系統維護功能，需要直接操縱SDE表的時候纔用到。
暫時只有這些，有遺漏的話以後再補充。

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Geodatabase應用程序編程接口（API）提供了許多不同的方式來查詢表和要素類。本主題介紹如何使用query filters, spatial filters, and QueryDefs對數據進行查詢。

1.IQueryFilter interface

// Create the query filter.  
IQueryFilter queryFilter = new QueryFilterClass();  

// Select the fields to be returned—the name and address of the businesses.  
queryFilter.SubFields = "NAME, ADDRESS";  

// Set the filter to return only restaurants.  
queryFilter.WhereClause = "TYPE = 'Restaurant'";  

// Use the PostfixClause to alphabetically order the set by name.  
IQueryFilterDefinition queryFilterDef = (IQueryFilterDefinition)queryFilter;  
queryFilterDef.PostfixClause = "ORDER BY NAME";  

// Output the returned names and addresses.  
int nameIndex = table.FindField("NAME");  
int addressIndex = table.FindField("ADDRESS");  
using (ComReleaser comReleaser = new ComReleaser())  
{  
  ICursor cursor = table.Search(queryFilter, true);  
  comReleaser.ManageLifetime(cursor);  
  IRow row = null;  
  while ((row = cursor.NextRow()) != null)  
  {  
    String name = Convert.ToString(row.get_Value(nameIndex));  
    String address = Convert.ToString(row.get_Value(addressIndex));  
    Console.WriteLine("{0} - {1}", name, address);  
  }  
} 

2.ISpatialFilter interface

// Create the envelope and define its position.  
IEnvelope envelope = new EnvelopeClass();  
envelope.PutCoords(-84.4078, 33.7787, -84.3856, 33.7997);  

// Create the spatial filter and set its spatial constraints.  
ISpatialFilter spatialFilter = new SpatialFilterClass  
{  
  Geometry = envelope,  
  GeometryField = featureClass.ShapeFieldName,  
  SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects  
};  

// Set the attribute constraints and subfields.  
// You want to exclude ramps, highways and interstates.  
spatialFilter.WhereClause = "NAME <> 'Ramp' AND PRE_TYPE NOT IN ('Hwy', 'I')";  
spatialFilter.SubFields = "NAME, TYPE";  

// Execute the query, displaying the roads returned.  
int nameIndex = featureClass.FindField("NAME");  
int typeIndex = featureClass.FindField("TYPE");  
using (ComReleaser comReleaser = new ComReleaser())  
{  
  IFeatureCursor featureCursor = featureClass.Search(spatialFilter, true);  
  comReleaser.ManageLifetime(featureCursor);  
  IFeature feature = null;  
  while ((feature = featureCursor.NextFeature()) != null)  
  {  
    String roadName = Convert.ToString(feature.get_Value(nameIndex));  
    String roadType = Convert.ToString(feature.get_Value(typeIndex));  
    Console.WriteLine("Name: {0}, Type: {1}", roadName, roadType);  
  }  
}  
//if a geometry bag is being used as the filter's query geometry, create a spatial index for the geometry bag before being assigned //to the geometry property. This can drastically increase the query's efficiency. The following code example shows how to do this:  

// Cast the bag to the ISpatialIndex interface.  
ISpatialIndex spatialIndex = (ISpatialIndex)geometryBag;  
spatialIndex.AllowIndexing = true;  
spatialIndex.Invalidate(); 

3.IQueryDef interface

// Create the QueryDef.  
IQueryDef2 queryDef2 = (IQueryDef2)featureWorkspace.CreateQueryDef();  

// Specify the table and fields to query.  
queryDef2.Tables = "Cities";  
queryDef2.SubFields = "Name, Pop1996";  
queryDef2.PostfixClause = "ORDER BY Pop1996 DESC";  


// Execute the query.  
using (ComReleaser comReleaser = new ComReleaser())  
{  
  ICursor cursor = queryDef2.Evaluate2(true);  
  comReleaser.ManageLifetime(cursor);  
  int nameIndex = cursor.FindField("Name");  
  int pop1996Index = cursor.FindField("Pop1996");  
  IRow row = null;  
  while ((row = cursor.NextRow()) != null)  
  {  
    String cityName = Convert.ToString(row.get_Value(nameIndex));  
    int population = Convert.ToInt32(row.get_Value(pop1996Index));  
    Console.WriteLine("{0}: {1}", cityName, population);  
  }  
}  

通過創建遊標QueryDef 可用於生成一個虛擬表或要素類。

// Create a reference to a TableQueryName object.  
IQueryName2 queryName2 = new TableQueryNameClass();  
queryName2.PrimaryKey = String.Empty;  

// Specify the query definition.  
queryName2.QueryDef = queryDef;  

// Get a name object for the workspace.  
IDataset dataset = (IDataset)workspace;  
IWorkspaceName workspaceName = (IWorkspaceName)dataset.FullName;  

// Cast the TableQueryName object to the IDatasetName interface and open it.  
IDatasetName datasetName = (IDatasetName)queryName2;  
datasetName.WorkspaceName = workspaceName;  
datasetName.Name = tableName;  
IName name = (IName)datasetName;  

// Open the name object and get a reference to a table object.  
ITable table = (ITable)name.Open();  

4.WHERE clauses