MDAC 2.5 SDK - ODBC Programmer's Reference
Chapter 7: Catalog Functions
A value list argument consists of a list of comma-separated values to be used for matching. There is only one value list argument in the ODBC catalog functions: the TableType argument in SQLTables. Setting TableType to a null pointer is the same as if it is set to SQL_ALL_TABLE_TYPES, which enumerates all possible members of the value list. This argument is not affected by the SQL_ATTR_METADATA_ID statement attribute. For more information, see the SQLTables function description.