请查阅以下2篇文档，看是否对您有帮助
https://eco.dameng.com/document/dm/zh-cn/app-dev/c_c++_dpi
https://eco.dameng.com/document/dm/zh-cn/pm/dpi-rogramming-guide.html

示例代码,注释中讲了如何使用DSQL_C_DEFAULT：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "DPI.h"
#include "DPIext.h"
#include "DPItypes.h"

#define DM_SVR "DM8"
#define DM_USER "SYSDBA"
#define DM_PWD "SYSDBA"

dhenv henv; /* 环境句柄 */
dhcon hcon; /* 连接句柄 */
dhstmt hstmt; /* 语句句柄 */
DPIRETURN rt; /* 函数返回值 */

/******************************************************
Notes：
获取错误信息
*******************************************************/
void dpi_err_msg_print(sdint2 hndl_type, dhandle hndl)
{
    sdint4 err_code;
    sdint2 msg_len;
    sdbyte err_msg[SDBYTE_MAX];

    /* 获取错误信息集合 */
    dpi_get_diag_rec(hndl_type, hndl, 1, &err_code, err_msg, sizeof(err_msg), &msg_len);
    printf("err_msg = %s, err_code = %d\n", err_msg, err_code);
}

/*
入口函数
*/
int main(int argc, char *argv[])
{
    sdbyte create_table_sql[] = "CREATE TABLE IF NOT EXISTS TEST.MY_TEST (C1 INT, C2 VARCHAR(10 CHAR))";
    sdbyte insert_sql[] = "INSERT INTO TEST.MY_TEST (C1, C2) VALUES (?, ?)";
    sdint4 in_c1;
    sdbyte in_c2[20] = {0};
    slength in_c1_ind_ptr, in_c2_ind_ptr;

    sdint4 out_c1 = 0;
    sdbyte out_c2[20] = {0};
    slength out_c1_ind = 0;
    slength out_c2_ind = 0;
    ulength row_num;

    char input[100];

    // 连接数据库
    rt = dpi_alloc_env(&henv);
    rt = dpi_alloc_con(henv, &hcon);
    rt = dpi_login(hcon, (sdbyte *)DM_SVR, (sdbyte *)DM_USER, (sdbyte *)DM_PWD);
    if (!DSQL_SUCCEEDED(rt))
    {
        dpi_err_msg_print(DSQL_HANDLE_DBC, hcon);
        return rt;
    }

    rt = dpi_alloc_stmt(hcon, &hstmt);

    // 创建表
    printf("创建表: TEST.MY_TEST...\n");
    rt = dpi_exec_direct(hstmt, create_table_sql);
    if (!DSQL_SUCCEEDED(rt))
    {
        dpi_err_msg_print(DSQL_HANDLE_STMT, hstmt);
    }
    else
    {
        printf("表创建成功。\n");
    }

    // 清空表，初始化测试环境
    printf("清空表: TEST.MY_TEST...\n");
    dpi_exec_direct(hstmt, (sdbyte *)"DELETE FROM TEST.MY_TEST");

    // 用户交互式插入数据
    while (1)
    {
        printf("请输入要插入的C1值（整数）或输入'q'退出：");
        fgets(input, sizeof(input), stdin);
        if (input[0] == 'q' || input[0] == 'Q')
            break;
        in_c1 = atoi(input);

        printf("请输入要插入的C2值（字符串，最多10字符）：");
        fgets(input, sizeof(input), stdin);
        input[strcspn(input, "\n")] = '\0'; // 去掉换行符
        strncpy((char *)in_c2, input, sizeof(in_c2) - 1);

        in_c1_ind_ptr = sizeof(in_c1);
        in_c2_ind_ptr = strlen((char *)in_c2);

        // 插入数据
        rt = dpi_prepare(hstmt, insert_sql);
        // 使用DSQL_C_DEFAULT来自动确认输入的数据类型。
        // dType则需要对应表中该列的数据类型
        rt = dpi_bind_param(hstmt, 1, DSQL_PARAM_INPUT, DSQL_C_DEFAULT, DSQL_INT, sizeof(in_c1), 0, &in_c1, sizeof(in_c1), &in_c1_ind_ptr);
         rt = dpi_bind_param(hstmt, 2, DSQL_PARAM_INPUT, DSQL_C_DEFAULT, DSQL_VARCHAR, sizeof(in_c2), 0, in_c2, sizeof(in_c2), &in_c2_ind_ptr);
        rt = dpi_exec(hstmt);
        if (!DSQL_SUCCEEDED(rt))
        {
            dpi_err_msg_print(DSQL_HANDLE_STMT, hstmt);
            return rt;
        }
        printf("数据插入成功: C1=%d, C2=%s\n", in_c1, in_c2);
    }

    // 查询数据
    dpi_exec_direct(hstmt, (sdbyte *)"SELECT * FROM TEST.MY_TEST");
    dpi_bind_col(hstmt, 1, DSQL_C_SLONG, &out_c1, sizeof(out_c1), &out_c1_ind);
    dpi_bind_col(hstmt, 2, DSQL_C_NCHAR, &out_c2, sizeof(out_c2), &out_c2_ind);

    printf("\n查询表中数据:\n");
    while (dpi_fetch(hstmt, &row_num) != DSQL_NO_DATA)
    {
        printf("C1 = %d, C2 = %s\n", out_c1, out_c2);
    }

    // 断开数据库连接
    rt = dpi_logout(hcon);
    if (!DSQL_SUCCEEDED(rt))
    {
        dpi_err_msg_print(DSQL_HANDLE_DBC, hcon);
        return rt;
    }

    rt = dpi_free_con(hcon);
    rt = dpi_free_env(henv);

    return rt;
}

编译指令(库文件路径写你本地的)：
gcc -g -DDM64 -I/home/dmdba/dmdbms/include -L/home/dmdba/dmdbms/bin -ldmdpi -o dpiBind dpi_bind.c
运行：
./dpiBind