使用ODBC访问数据库(二)

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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

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.

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