需要找到DB列的类型

这是我的代码片段。我得到了数据库中存在的所有表名和列名。现在我需要知道列的类型。比如它的int或varchar或其他什么。可以帮助我吗？ 顺便说一下这是C＃。

OleDbConnection con = new OleDbConnection(connectionString); DataTable schemaCols; DataTable schemaTbl; List tablesnames = new List(); string returnString=""; try { con.Open(); object[] objArrRestrict; objArrRestrict = new object[] { null, null, null, "TABLE" }; schemaTbl = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, objArrRestrict); foreach (DataRow row in schemaTbl.Rows) { tablesnames.Add(row["TABLE_NAME"].ToString()); } List columnnames = new List(); foreach (string str in tablesnames) { string selTbl = str; //con.Open(); object[] objArrRestrictNew; objArrRestrictNew = new object[] { null, null, selTbl, null }; // schemaCols = con.GetOleDbSchemaTable(OleDbSchemaGuid.Columns, objArrRestrictNew); foreach (DataRow row in schemaCols.Rows) { columnnames.Add(row["COLUMN_NAME"].ToString()); } } } 

Answer 1

您可以这样做的一种方法是使用OleDbCommand.ExecuteReader来读取您找到的每个表的架构。

  OleDbConnection con = new OleDbConnection(connectionString); DataSet tablesFromDB = new DataSet(); DataTable schemaTbl; try { // Open the connection con.Open(); object[] objArrRestrict = new object[] { null, null, null, "TABLE" }; // Get the table names from the database we're connected to schemaTbl = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, objArrRestrict); // Not sure if this is correct syntax...fix it if it isn't :) String commandText = @"SELECT * FROM {0}"; // Get each table name that we just found and get the schema for that table. foreach (DataRow row in schemaTbl) { DataTable dt = new DataTable(); OleDbCommand command = new OleDbCommand(String.Format(commandText, row["TABLE_NAME"] as String), con); dt.Load(command.ExecuteReader(CommandBehavior.SchemaOnly)); tablesFromDB.Tables.Add(dt); } } 

这样，您可以遍历DataSet的DataTable集合并获取列名和列字段类型。

 foreach (DataTable dt in tablesFromDB) { foreach (DataColumn dc in dt.Columns) { // Do something with the column names and types here // dc.ColumnName is the column name for the current table // dc.DataType.ToString() is the name of the type of data in the column } } 

可能有更好的方法，但我认为这是一个开始。

Answer 2

您也可以从OleDb检索列类型

 DataTable schemaTable = connection.GetOleDbSchemaTable( System.Data.OleDb.OleDbSchemaGuid.Columns, new object[] { null, null, null, null }); 

schemaTable的DATA_TYPE列包含可以强制转换为OleDbType的整数

如果你需要数据类型，你可以使用类似于此的转换函数（我将它用于mdb和accdb文件，但我知道它应该被增强）

  private static string ConvertToJetDataType(int oleDbDataType) { switch (((OleDbType)oleDbDataType)) { case OleDbType.LongVarChar: return "varchar"; case OleDbType.BigInt: return "int"; // In Jet this is 32 bit while bigint is 64 bits case OleDbType.Binary: case OleDbType.LongVarBinary: return "binary"; case OleDbType.Boolean: return "bit"; case OleDbType.Char: return "char"; case OleDbType.Currency: return "decimal"; case OleDbType.DBDate: case OleDbType.Date: case OleDbType.DBTimeStamp: return "datetime"; case OleDbType.Decimal: case OleDbType.Numeric: return "decimal"; case OleDbType.Double: return "double"; case OleDbType.Integer: return "int"; case OleDbType.Single: return "single"; case OleDbType.SmallInt: return "smallint"; case OleDbType.TinyInt: return "smallint"; // Signed byte not handled by jet so we need 16 bits case OleDbType.UnsignedTinyInt: return "byte"; case OleDbType.VarBinary: return "varbinary"; case OleDbType.VarChar: return "varchar"; case OleDbType.BSTR: case OleDbType.Variant: case OleDbType.VarWChar: case OleDbType.VarNumeric: case OleDbType.Error: case OleDbType.WChar: case OleDbType.DBTime: case OleDbType.Empty: case OleDbType.Filetime: case OleDbType.Guid: case OleDbType.IDispatch: case OleDbType.IUnknown: case OleDbType.UnsignedBigInt: case OleDbType.UnsignedInt: case OleDbType.UnsignedSmallInt: case OleDbType.PropVariant: default: throw new ArgumentException(string.Format("The data type {0} is not handled by Jet. Did you retrieve this from Jet?", ((OleDbType)oleDbDataType))); } } 

Answer 3

这对你有所帮助（参见C＃语法）：

http://msdn.microsoft.com/en-us/library/system.data.datacolumn.datatype(VS.71).aspx

Answer 4

试试这个:(不需要使用SQL的select语句）

 string connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + dataSource; OleDbConnection connection = new OleDbConnection(connectionString); DataTable schemaTable = null; string tblName = "xxx"; try { connection.Open(); //obtain column information in table "xxx" schemaTable = connection.GetOleDbSchemaTable(OleDbSchemaGuid.Columns, new object[] { null, null, tblName, null }); } catch (Exception ex) { String str = ex.Message; } finally { connection.Close(); } foreach (DataRow row in schemaTable.Rows) { columnNames.Add(row["COLUMN_NAME"].ToString()); DataColumn colnum_type = row.Table.Columns["DATA_TYPE"] as DataColumn; //note this line ColumnDataTypes.Add(colnum_type.DataType); }