使用C/C++语言开发，那么必定会在与ODBC语言间存在数据的转换的问题，因为ODBC所存在的一些数据类型在C语言中是不存在的。所以在ODBC的开发过程中不要使用int，float之类的C语言的实际类型来定义变量而应该使用ODBC定义的数据类型来定义变量，如SQLINTEGER，SQLFLOAT。在ODBC以宏定义的方式定义了C语言和ODBC中使用的数据类型：
C type identifier
ODBC C typedef
C type
SQL_C_CHAR
SQLCHAR *
unsigned char *
SQL_C_SSHORT
SQLSMALLINT
short int
SQL_C_USHORT
SQLUSMALLINT
unsigned short int
SQL_C_SLONG
SQLINTEGER
long int
SQL_C_ULONG
SQLUINTEGER
unsigned long int
SQL_C_FLOAT
SQLREAL
float
SQL_C_DOUBLE
SQLDOUBLE, SQLFLOAT
double
SQL_C_BIT
SQLCHAR
unsigned char
SQL_C_STINYINT
SQLSCHAR
signed char
SQL_C_UTINYINT
SQLCHAR
unsigned char
SQL_C_SBIGINT
SQLBIGINT
_int64[h]
SQL_C_UBIGINT
SQLUBIGINT
unsigned _int64
SQL_C_BINARY
SQLCHAR *
unsigned char *
SQL_C_XML
SQLCHAR *
unsigned char *
SQL_C_BOOKMARK
BOOKMARK
unsigned long int
SQL_C_VARBOOKMARK
SQLCHAR *
unsigned char *
SQL_C_TYPE_DATE
SQL_DATE_STRUCT
struct tagDATE_STRUCT {
SQLSMALLINT year;
SQLUSMALLINT month;
SQLUSMALLINT day;
} DATE_STRUCT;
SQL_C_TYPE_TIME
SQL_TIME_STRUCT
struct tagTIME_STRUCT {
SQLUSMALLINT hour;
SQLUSMALLINT minute;
SQLUSMALLINT second;
} TIME_STRUCT;
SQL_C_TYPE_TIMESTAMP
SQL_TIMESTAMP_STRUCT
struct tagTIMESTAMP_STRUCT {
SQLSMALLINT year;
SQLUSMALLINT month;
SQLUSMALLINT day;
SQLUSMALLINT hour;
SQLUSMALLINT minute;
SQLUSMALLINT second;
SQLUINTEGER fraction;
} TIMESTAMP_STRUCT
SQL_C_NUMERIC
SQL_NUMERIC_STRUCT
struct tagSQL_NUMERIC_STRUCT {
SQLCHAR precision;
SQLSCHAR scale;
SQLCHAR sign;
SQLCHAR
val[SQL_MAX_NUMERIC_LEN];
} SQL_NUMERIC_STRUCT;
SQL_C_GUID
SQLGUID
struct tagSQLGUID {
DWORD Data1;
WORD Data2;
WORD Data3;
BYTE Data4[8];
} SQLGUID;
All C interval data types
SQL_INTERVAL_STRUCT
See the "C Interval Structure" section, later in this appendix.
