VistaDB 6
VistaDB / Developer's Guide / SQL Reference / Database Schema / VistaDBDataReader GetSchemaTable example
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    VistaDBDataReader GetSchemaTable example
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    The VistaDBDataReader class's GetSchemaTable method is similar to using a DataTable FillSchema method. Each method lets you create a DataTable contains DataColumn objects that correspond to the columns returned by your query. The GetSchemaTable method accepts no parameters and returns a new DataTable object.

    The purpose of the GetSchemaTable call is to allow you to pull schema information based upon a query. You build up the query, but rather than executing it normally you tell the provider to get just the schema for the query (it is not actually run).

    VistaDBDataReader myReader = cmd.ExecuteReader( CommandBehavior.SchemaOnly ); 

    Setting the CommandBehavior to SchemaOnly will make a complete round trip to the database, load the schema and it's information into the reader. Then you can call the Reader with the GetSchemaTable to get the information into a useable format.

    DataTable schemaTable = myReader.GetSchemaTable(); 

    Now the schemaTable can be walked to determine what the provider said about the query.


    Example Title
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    // This example loads the employees table from Northwind
    static void Main( string[] args )
       string dbName = @"C:\Users\Public\Documents\VistaDB 6\Databases\Northwind.vdb6";
       string[] restrictions = new string[4] { null, null, "Employees", null };
       using (VistaDB.Provider.VistaDBConnection connection = new VistaDB.Provider.VistaDBConnection( "Data Source=" + dbName ))
          using (VistaDBCommand cmd = new VistaDBCommand("Select * from Employees", connection))
             using (VistaDBDataReader myReader =
                   cmd.ExecuteReader( CommandBehavior.SchemaOnly ))
                //Retrieve column schema into a DataTable.
                DataTable schemaTable = myReader.GetSchemaTable();
                foreach (DataRow myField in schemaTable.Rows)
                   foreach (DataColumn myProperty in schemaTable.Columns)
                           Console.WriteLine(myProperty.ColumnName + " = " +

    The above will output a console list like this listed below for each column in the table.

    ColumnName = EmployeeID
    ColumnOrdinal = 0
    ColumnSize = 4
    NumericPrecision = 255
    NumericScale = 255
    IsUnique = True
    IsKey = True
    BaseServerName = 
    BaseCatalogName = 
    BaseColumnName = EmployeeID
    BaseSchemaName = 
    BaseTableName = Employees
    DataType = System.Int32
    AllowDBNull = False
    ProviderType = 10
    IsAliased = False
    IsExpression = False
    IsIdentity = True
    IsAutoIncrement = True
    IsRowVersion = False
    IsHidden = False
    IsLong = False
    IsReadOnly = False
    ProviderSpecificDataType = System.Int32
    DefaultValue = 
    DataTypeName = Int
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