MDAC 2.5 SDK - ODBC Programmer's Reference
Chapter 6: Connecting to a Data Source or Driver

Declaring the Application's ODBC Version

Before an application allocates a connection, it must set the SQL_ATTR_ODBC_VERSION environment attribute. This attribute states that the application follows the ODBC 2.x or ODBC 3.x specification when using the following items:

• SQLSTATEs. Many SQLSTATE values are different in ODBC 2.x and ODBC 3.x.
  
  
• Date, Time, and Timestamp Type Identifiers. The following table shows the type identifiers for date, time, and timestamp data in ODBC 2.x and ODBC 3.x.

  ODBC 2.x	ODBC 3.x
  SQL Type Identifiers
  SQL_DATE	SQL_TYPE_DATE
  SQL_TIME	SQL_TYPE_TIME
  SQL_TIMESTAMP	SQL_TYPE_TIMESTAMP
  C Type Identifiers
  SQL_C_DATE	SQL_C_TYPE_DATE
  SQL_C_TIME	SQL_C_TYPE_TIME
  SQL_C_TIMESTAMP	SQL_C_TYPE_TIMESTAMP

  
  
• CatalogName Argument in SQLTables. In ODBC 2.x, the wildcard characters ("%" and "_") in the CatalogName argument are treated literally. In ODBC 3.x, they are treated as wildcard characters. Thus, an application that follows the ODBC 2.x specification cannot use these as wildcard characters and does not escape them when using them as literals. An application that follows the ODBC 3.x specification can use these as wildcard characters or escape them and use them as literals. For more information, see "Arguments in Catalog Functions" in Chapter 7, "Catalog Functions."

The ODBC 3.x Driver Manager and ODBC 3.x drivers check the version of the ODBC specification to which an application is written and respond accordingly. For example, if the application follows the ODBC 2.x specification and calls SQLExecute before calling SQLPrepare, the ODBC 3.x Driver Manager returns SQLSTATE S1010 (Function sequence error). If the application follows the ODBC 3.x specification, the Driver Manager returns SQLSTATE HY010 (Function sequence error). For more information, see "Backward Compatibility and Standards Compliance" in Chapter 17, "Programming Considerations."

Important   Applications that follow the ODBC 3.x specification must use conditional code to avoid using functionality new to ODBC 3.x when working with ODBC 2.x drivers. ODBC 2.x drivers do not support functionality new to ODBC 3.x just because the application declares that it follows the ODBC 3.x specification. Furthermore, ODBC 3.x drivers do not cease to support functionality new to ODBC 3.x just because the application declares that it follows the ODBC 2.x specification.