使用ODBC訪問資料庫(二)

        使用C/C++語言開發，那麼必定會在與ODBC語言間存在資料的轉換的問題，因為ODBC所存在的一些資料類型在C語言中是不存在的。所以在ODBC的開發過程中不要使用int，float之類的C語言的實際類型來定義變數而應該使用ODBC定義的資料類型來定義變數，如SQLINTEGER，SQLFLOAT。在ODBC以宏定義的方式定義了C語言和ODBC中使用的資料類型：

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
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.