如何使用VFPOLEDB获取DBF信息

Question

我可以使用GetSchemaTable和GetXMLSchema获取有关字段类型,大小等的信息来自使用VFPOLEDB打开的Foxpro DBF,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,只是构建索引的标准,以帮助我生成SQL命令以在SQL服务器上创建表并导入数据.

我可以DISPLAY STRUCTURE对所有表上的文本文件进行输出并在VB.NET中解析它,但我希望有一些我可以忽略的东西,因为我还不熟悉VB.NET/OLEDB语法.

Answer 1

一些研究泄露了这些结果。我首先查看了ForeignKey.FKTableSchemaProperty，不幸的是不是 .NET 属性。后来，当我发现OleDbSchemaGuid.Indexes 字段时，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的方法。最终下面的文章照亮了道路，

GetOleDbSchemaTable(OleDb.OleDbSchemaGuid.Indexes - 如何访问索引上包含的列

和这个发现

OleDb 和 Odbc 提供程序不提供将返回非键（“包含”）索引列的内置目录方法。

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 查询架构表来实现的。以下示例是在Employees著名Northwind示例数据库的表上进行的。干得好，

//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();

最后的结果，

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

然而，后来通过删除限制，我设法克服了该提供商不支持的方法。错误并最终总结为这个更短的解决方案，

//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();
}

这会导致更长的输出需要整理，但其中一部分是

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