结构体dfield_t

/* SQL data field struct */
typedef struct dfield_struct     dfield_t;

/** Structure for an SQL data field */
struct dfield_struct{
    void*        data;    /*!< pointer to data */
    unsigned    ext:;    /*!< TRUE=externally stored, FALSE=local */
    unsigned    len:;    /*!< data length; UNIV_SQL_NULL if SQL null */
    dtype_t        type;    /*!< type of data */
};