用ArcEngine的接口做过查询统计的同学应该知道，由于ArcEngine并没有完整支持SQL，所以做简单的查询还好，稍微复杂一点就开始捉襟见肘了。
现在总结一下几种查询的方法：
1.IQueryFilter、ISpatialFilter接口。
这是最常见的，把参数设置进去，然后调用IFeatureClass或者ITable的Search方法就行。可以转为IQueryFilterDefinition接口设置Order By和Group By语句。
2.IQueryDef接口。
个人觉得这个接口最方便，可以设置多表查询。虽然有些帮助文档说不能使用Order By和Group By语句，但是其实是可以的，比如可以这样设置：
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”;
但是这个接口只可以用在GeoDatabase，不能用于ShapeFile和Coverage数据。
3.使用IDataStatistics接口，然后调用Statistics方法返回IStatisticsResults对象，可以获取六种统计结果。
4.另外还要加一种方法，就是IWorkspace.ExecuteSQL，可以直接输入SQL语句，但是这个方法没有返回值，不能获取结果，所以只有在做一些系统维护功能，需要直接操纵SDE表的时候才用到。
暂时只有这些，有遗漏的话以后再补充。
Geodatabase应用程序编程接口（API）提供了许多不同的方式来查询表和要素类。本主题介绍如何使用query filters, spatial filters, and QueryDefs对数据进行查询。
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);
}
}
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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();
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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);
}
}
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通过创建游标QueryDef 可用于生成一个虚拟表或要素类。
// 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();
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4.WHERE clauses
---------------------
作者：sRhee
来源：CSDN
原文：https://blog.csdn.net/srhee/article/details/79036578
版权声明：本文为博主原创文章，转载请附上博文链接！