title: "Record Field Exchange: Working with the Wizard Code"

helpviewer_keywords: ["DoFieldExchange method, overriding", "Unicode, with database classes", "field data members, declaring", "RFX (ODBC), wizard code", "RFX (ODBC), implementing", "field data members", "ODBC, RFX", "m_nParams data member, initializing", "m_nFields data member", "m_nParams data member", "overriding, DoFieldExchange", "m_nFields data member, initializing"]

ms.assetid: f00d882a-ff1b-4a75-9717-98d8762bb237

This topic explains the code that the MFC Application Wizard and **Add Class** (as described in [Adding an MFC ODBC Consumer](../../mfc/reference/adding-an-mfc-odbc-consumer.md)) write to support RFX and how you might want to alter that code.

When you use the [MFC ODBC Consumer Wizard](../../mfc/reference/adding-an-mfc-odbc-consumer.md) from **Add Class** wizard to declare a recordset class derived from `CRecordset`, the resulting class has the general structure shown in the following simple class:

title: "Recordset: Creating and Closing Recordsets (ODBC)"

helpviewer_keywords: ["ODBC recordsets, creating", "recordsets, creating", "recordsets, opening", "recordsets, closing", "ODBC recordsets, closing", "ODBC recordsets, opening"]

ms.assetid: 8d2aac23-4396-4ce2-8c60-5ecf1b360d3d

This topic applies to the MFC ODBC classes.

To use a recordset, construct a recordset object and then call its `Open` member function to run the recordset's query and select records. When you finish with the recordset, close and destroy the object.

title: "Recordset: Declaring a Class for a Predefined Query (ODBC)"

helpviewer_keywords: ["ODBC recordsets, queries", "predefined queries and recordsets", "stored procedures, and recordsets", "recordsets, predefined queries", "recordsets, stored procedures"]

ms.assetid: d27c4df9-dad2-4484-ba72-92ab0c8ff928

This topic applies to the MFC ODBC classes.

This topic explains how to create a recordset class for a predefined query (sometimes called a stored procedure, as in Microsoft SQL Server).

title: "Recordset: Declaring a Class for a Table (ODBC)"

helpviewer_keywords: ["ODBC recordsets, declaring class for tables", "recordsets, declaring classes for tables"]

ms.assetid: 3fe286c2-3f3d-493d-9d8c-762310939d08

This topic applies to the MFC ODBC classes.

The most common recordset class opens a single table. To declare a recordset class for a single table, use the [MFC ODBC Consumer Wizard](../../mfc/reference/adding-an-mfc-odbc-consumer.md) from **Add Class** and choose each column you want by naming a corresponding recordset field data member.

title: "Recordset: Dynamically Binding Data Columns (ODBC)"

helpviewer_keywords: ["ODBC recordsets [C++], binding columns dynamically", "data binding [C++], recordset columns", "recordsets [C++], binding data", "data binding [C++], columns in recordsets", "columns [C++], binding to recordsets"]

ms.assetid: bff67254-d953-4ae4-9716-91c348cb840b

At design time, the MFC Application Wizard or [MFC ODBC Consumer Wizard](../../mfc/reference/adding-an-mfc-odbc-consumer.md) (from **Add Class**) creates recordset classes based on the known tables and columns on your data source. Databases can change between when you design them and later when your application uses those tables and columns at run time. You or another user might add or drop a table or add or drop columns from a table that your application's recordset relies on. This probably is not a concern for all data-access applications, but if it is for yours, how can you cope with changes in the database schema, other than by redesigning and recompiling? The purpose of this topic is to answer that question.

This topic describes the most common case in which you might bind columns dynamically — having begun with a recordset based on a known database schema, you want to handle additional columns at run time. The topic further assumes that the additional columns map to `CString` field data members, the most common case, although suggestions are supplied to help you manage other data types.

title: "Recordset: How Recordsets Select Records (ODBC)"

helpviewer_keywords: ["recordsets, selecting records", "record selection, ODBC recordsets", "SQL statements, recordset", "records, selecting", "recordsets, constructing SQL statements", "ODBC recordsets, selecting records"]

ms.assetid: 343a6a91-aa4c-4ef7-b21f-2f2bfd0d3787

This topic applies to the MFC ODBC classes.

This topic explains:

This topic applies to the MFC ODBC classes.

This topic explains how to obtain aggregate results using the following [SQL](../../data/odbc/sql.md) keywords:

title: "Recordset (ODBC)"

helpviewer_keywords: ["recordsets, snapshots", "recordsets, creating", "dynamic recordsets", "forward-only recordsets", "recordsets, dynasets", "ODBC recordsets, CRecordset objects", "ODBC recordsets", "recordsets, about recordsets", "snapshots, ODBC recordsets", "dynasets"]

ms.assetid: 333337c5-575e-4d26-b5f6-47166ad7874d

An example of a recordset based on a table is "all customers," which accesses a Customer table. An example of a query is "all invoices for Joe Smith." An example of a recordset based on a stored procedure (sometimes called a predefined query) is "all of the delinquent accounts," which invokes a stored procedure in the back-end database. A recordset can join two or more tables from the same data source, but not tables from different data sources.