我可以使用GetSchemaTable 和GetXMLSchema 从使用 VFPOLEDB 打开的 Foxpro DBF 中获取有关字段类型、大小等的信息，但无法获取有关表/CDX 中的索引的任何信息。
我不想使用索引，只是建立索引的条件来帮助我生成 SQL 命令以在 SQL 服务器上创建表并导入数据。
我可以将DISPLAY STRUCTURE 输出到所有表上的文本文件并在 VB.NET 中解析它，但我希望有一些我忽略的东西，因为我对 VB.NET/OLEDB 语法不太熟悉还没有。
【问题讨论】：
标签： vb.net oledb foxpro visual-foxpro
一点点研究就泄露了这些结果。我开始查看ForeignKey.FKTableSchema 属性，不幸的是不是.NET 属性。后来，当我找到 OleDbSchemaGuid.Indexes Field 时，一切看起来都很好，直到我运行应用程序并得到 此提供程序不支持该方法。 最终，以下文章点亮一路走来，
GetOleDbSchemaTable(OleDb.OleDbSchemaGuid.Indexes - How to access included columns on index
这个发现
OleDb 和 Odbc 提供程序不提供内置目录方法 这将返回非键（“包含”）索引列。
然而，这是一些非常有趣的建议，可以让您编写这个小控制台应用程序来获取表中可用的索引。这是通过直接从 SQL 查询模式表来实现的。以下示例在著名的Northwind 示例数据库的Employees 表上。给你，
//Open a connection to the SQL Server Northwind database.
var connectionString =
"Provider=SQLOLEDB;Data Source=SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=SSPI;Encrypt=False;TrustServerCertificate=False";
using (var connection = new OleDbConnection(connectionString))
{
connection.Open();
var select = "SELECT " +
" T.name AS TABLE_NAME" +
" , IX.name AS INDEX_NAME" +
" , IC.index_column_id AS IX_COL_ID" +
" , C.name AS COLUMN_NAME" +
" , IC.is_included_column AS INCLUDED_NONKEY" +
" " +
"FROM " +
" sys.tables T " +
" INNER JOIN sys.indexes IX" +
" ON T.object_id = IX.object_id " +
" INNER JOIN sys.index_columns IC" +
" ON IX.object_id = IC.object_id " +
" AND IX.index_id = IC.index_id " +
" INNER JOIN sys.columns C" +
" ON IC.object_id = C.object_id " +
" AND IC.column_id = C.column_id " +
" " +
"WHERE T.name = 'Employees'" +
"ORDER BY IC.index_column_id";
OleDbCommand cmd = new OleDbCommand(@select, connection);
cmd.CommandType = CommandType.Text;
var outputTable = new DataSet("Table");
var my = new OleDbDataAdapter(cmd).Fill(outputTable);
foreach (DataTable table in outputTable.Tables)
{
foreach (DataRow myField in table.Rows)
{
//For each property of the field...
foreach (DataColumn myProperty in table.Columns)
{
//Display the field name and value.
Console.WriteLine(myProperty.ColumnName + " = " +
myField[myProperty].ToString());
}
Console.WriteLine();
}
}
}
Console.ReadLine();
最后是结果，
TABLE_NAME = Employees
INDEX_NAME = PK_Employees
IX_COL_ID = 1
COLUMN_NAME = EmployeeID
INCLUDED_NONKEY = False
TABLE_NAME = Employees
INDEX_NAME = LastName
IX_COL_ID = 1
COLUMN_NAME = LastName
INCLUDED_NONKEY = False
TABLE_NAME = Employees
INDEX_NAME = PostalCode
IX_COL_ID = 1
COLUMN_NAME = PostalCode
INCLUDED_NONKEY = False
但是，后来通过删除限制，我设法克服了 此提供程序不支持该方法。 错误并最终将其总结为这个较短的解决方案,
//Open a connection to the SQL Server Northwind database.
var connectionString =
"Provider=SQLOLEDB;Data Source=SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=SSPI;Encrypt=False;TrustServerCertificate=False";
using (OleDbConnection cnn = new OleDbConnection(connectionString))
{
cnn.Open();
DataTable schemaIndexess = cnn.GetSchema("Indexes",
new string[] {null, null, null});
DataTable schemaIndexes = cnn.GetOleDbSchemaTable(
OleDbSchemaGuid.Indexes,
new object[] {null, null, null});
foreach (DataRow myField in schemaIndexes.Rows)
{
//For each property of the field...
foreach (DataColumn myProperty in schemaIndexes.Columns)
{
//Display the field name and value.
Console.WriteLine(myProperty.ColumnName + " = " +
myField[myProperty].ToString());
}
Console.WriteLine();
}
Console.ReadLine();
}
哪些结果需要整理出更长的输出，但其中的一部分会是
TABLE_CATALOG = Northwind
TABLE_SCHEMA = dbo
TABLE_NAME = Employees
INDEX_CATALOG = Northwind
INDEX_SCHEMA = dbo
INDEX_NAME = LastName
PRIMARY_KEY = False
UNIQUE = False
CLUSTERED = False
TYPE = 1
FILL_FACTOR = 0
INITIAL_SIZE =
NULLS =
SORT_BOOKMARKS = False
AUTO_UPDATE = True
NULL_COLLATION = 4
ORDINAL_POSITION = 1
COLUMN_NAME = LastName
COLUMN_GUID =
COLUMN_PROPID =
COLLATION = 1
CARDINALITY =
PAGES = 1
FILTER_CONDITION =
INTEGRATED = False
【讨论】：
完美！ 我需要提取的一切。由于它在 vb.net 部分中，我发布了我的粗略代码，我过滤了返回的字段，因此我可以在这里列出一些。 它返回与索引相关的所有相关信息，甚至是使用表达式创建的复杂信息。 将返回带有 CDX 索引的连接字符串中提供的路径中的所有表。
TABLE_NAME = schematest
INDEX_NAME = char3ascen
NULLS = 1
EXPRESSION = char3ascen
TABLE_NAME = schematest
INDEX_NAME = expressn
NULLS = 2
EXPRESSION = LEFT(char1null,4)+SUBSTR(char2,4,2)
TABLE_NAME = schematest
INDEX_NAME = multifld
NULLS = 2
EXPRESSION = char1null+char2
TABLE_NAME = customer
INDEX_NAME = zip
NULLS = 1
EXPRESSION = zip
Private Sub GetIndexInfo_Click(sender As Object, e As EventArgs) Handles GetIndexInfo.Click
Dim cnnOLEDB As New OleDbConnection
Dim SchemaTable As DataTable
Dim myField As DataRow
Dim myProperty As DataColumn
Dim ColumnNames As New List(Of String)
Dim strConnectionString = "Provider=vfpoledb;Data Source=D:\ACW\;Collating Sequence=general;DELETED=False"
cnnOLEDB.ConnectionString = strConnectionString
cnnOLEDB.Open()
ColumnNames.Add("TABLE_NAME")
columnnames.Add("INDEX_NAME")
columnnames.Add("NULLS")
columnnames.Add("TYPE")
columnnames.Add("EXPRESSION")
SchemaTable = cnnOLEDB.GetSchema("Indexes")
'For Each myProperty In SchemaTable.Columns
For Each myField In SchemaTable.Rows
For Each myProperty In SchemaTable.Columns
If ColumnNames.Contains(myProperty.ColumnName) Then
Console.WriteLine(myProperty.ColumnName & " = " & myField(myProperty).ToString)
End If
Next
Console.WriteLine()
Next
Console.ReadLine()
DGVSchema.DataSource = SchemaTable
End Sub
【讨论】：