Use ODBC to access the database (2)

If you use C/C ++ for development, there will be a data conversion problem between ODBC and ODBC, because some ODBC data types do not exist in C. Therefore, do not use int, float or other types of C language to define variables during ODBC development. Instead, use the data types defined by ODBC to define variables, such as sqlinteger and sqlfloat. ODBC defines the data types used in the C language and ODBC in macro-defined mode:

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.