MySQL BLOB 记录的读写， MySQL 5.0.91, WIN11, VS2022

1. VS2022  控制台工程，Debug X86模式，字符集选用Multi-Byte

2. 把MySQL的头文件和库文件路径加进工程。

3. 把MySQL的库目录中的动态链接库libmysql.dll 复制到工程的当前工作目录下

4. 创建表，data 字段是blob 类型，

5. 定义一段数据 100个字节， 0x55，0xaa开头， 0x55，0xaa结尾。

6. 把数据插入数据库。

7. 读出数据，打印头尾的数据验证结果。

程序运行效果：

程序 MySQLTest2.cpp

// MySQLTest2.cpp : This file contains the 'main' function. Program execution begins and ends there.
// C读写MySQL BLOB数据
// XGZ 2022-07-16 SZ

#include <WinSock2.h>
#include <mysql.h>
#include <stdio.h>


#pragma comment(lib,"libmysql.lib")

int main()
{
    MYSQL* conn;
    MYSQL_ROW row;
    MYSQL_RES* res;
    int    nrow;
    int    ncolum;

    conn = mysql_init(NULL);
    if (!conn)
    {
        printf("/n <ERR> mysql_init failed!");
        return -1;
    }
    //本地连接到test数据库
    conn = mysql_real_connect(conn, "127.0.0.1", "root", "root", "test", 0, NULL, 0);
    if (conn)
    {
        printf("/n<OK>mysql_real_connect success!");
    }
    else
    {
        printf("/n<ERR>mysql_real_connect failed!");
        return -1;
    }
    
    //创建表
   if (mysql_query(conn, "create table testb (name varchar(256), data blob, size int);") != 0)
    {
        printf("/n Create failed");
        return -1;
    }

   //插入数据 0================================
  
    MYSQL_STMT* stmt = mysql_stmt_init(conn);
    MYSQL_BIND bind[3] ={0};
    char  value[100];
    char  name[256];
    int   length;

    strcpy_s(name, 256, "name123");
    

    memset(value, 0, 100);
    value[0] = 0x55;
    value[1] = 0xaa;
    value[98] = 0x55;
    value[99] = 0xaa;

    length = 100;

    if (!stmt) return -1;
    char sql2[1024] = "insert into testb (name,data,size) values(?,?,?);";
    if (mysql_stmt_prepare(stmt, sql2, strlen(sql2))) return -1;

    bind[0].buffer_type = MYSQL_TYPE_STRING;
    bind[0].buffer = name;
    bind[0].buffer_length = strlen(name);

    bind[1].buffer_type = MYSQL_TYPE_BLOB;
    bind[1].buffer = value;
    bind[1].buffer_length = length;

    bind[2].buffer_type = MYSQL_TYPE_LONG;
    bind[2].buffer = &length;
   
    if (mysql_stmt_bind_param(stmt, bind) != 0) return -1;
    if (mysql_stmt_execute(stmt) != 0) return -1;
    mysql_stmt_close(stmt);

    //===============================
    //查询test数据库user表
    mysql_query(conn, "select * from testb");
    res = mysql_store_result(conn);
    if (NULL == res)
    {
        return 0;
    }

    ncolum = mysql_num_fields(res);  
    nrow = mysql_num_rows(res);
    
    printf("/nncolum=%d,count=%d", ncolum, nrow);

    //读取并打印数据
    while (row = mysql_fetch_row(res))
    {
        printf("/n name= %s", row[0]);
        printf("/n data = %2X,%2X,%2X ....%2X,%2X,%2X",
            row[1][0], row[1][1], row[1][2],
            row[1][97], row[1][98], row[1][99] );

        printf("/n size = %d", atoi(row[2]));

    }
    
    mysql_close(conn);
    return 0;
}