Assembly: System.Data (in System.Data.dll)
The OLE DB.NET Framework Data Provider uses positional parameters that are marked with a question mark (?) instead of named parameters.
When querying an Oracle database using the Microsoft OLE DB Provider for Oracle (MSDAORA) and the OLE DB.NET Framework Data Provider, using the LIKE clause to query values in fixed-length fields may not return all expected matches. The reason is that when Oracle matches values for fixed-length fields in a LIKE clause, it matches the entire length of the string, including any padding trailing spaces. For example, if a table in an Oracle database contains a field named "Field1" that is defined as char(3), and you enter the value "a" into a row of that table, the following code does not return the row.
Dim queryString As String = "SELECT * FROM Table1 WHERE Field1 LIKE ?" Dim command As OleDbCommand = New OleDbCommand(queryString, connection) command.Parameters.Add("@p1", OleDbType.Char, 3).Value = "a" Dim reader As OleDbDataReader = command.ExecuteReader()
This is because Oracle stores the column value as "a " (padding "a", with trailing spaces, to the fixed field length of 3), which Oracle does not treat as a match for the parameter value of "a" in the case of a LIKE comparison of fixed-length fields.
To resolve this problem, append a percentage ("%") wildcard character to the parameter value ("a%"), or use an SQL = comparison instead.
The following example creates multiple instances of through the OleDbParameterCollection collection within the OleDbDataAdapter. These parameters are used to select data from the data source and place the data in the DataSet. This example assumes that a DataSet and an OleDbDataAdapter have already been created by using the appropriate schema, commands, and connection.
Public Function GetDataSetFromAdapter( _ ByVal dataSet As DataSet, ByVal connectionString As String, _ ByVal queryString As String) As DataSet Using connection As New OleDbConnection(connectionString) Dim adapter As New OleDbDataAdapter(queryString, connection) ' Set the parameters. adapter.SelectCommand.Parameters.Add( _ "@CategoryName", OleDbType.VarChar, 80).Value = "toasters" adapter.SelectCommand.Parameters.Add( _ "@SerialNum", OleDbType.Integer).Value = 239 ' Open the connection and fill the DataSet. Try connection.Open() adapter.Fill(dataSet) Catch ex As Exception Console.WriteLine(ex.Message) End Try ' The connection is automatically closed when the ' code exits the Using block. End Using Return dataSet End Function
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.