vue3+koa+mysql实现图片上传，具体怎么实现，分别写前端和后端的例子代码、

对于Vue3+Koa+MySQL实现图片上传，下面是前端和后端的示例代码：

前端代码（使用Vue3）：

<template>
  <div>
    <input type="file" @change="handleFileUpload" />
    <button @click="uploadImage">上传图片</button>
  </div>
</template>

<script>
import axios from "axios";

export default {
  data() {
    return {
      selectedFile: null,
    };
  },
  methods: {
    handleFileUpload(event) {
      this.selectedFile = event.target.files[0];
    },
    uploadImage() {
      const formData = new FormData();
      formData.append("image", this.selectedFile);

      axios.post("http://localhost:3000/upload", formData)
        .then(response => {
          console.log(response.data);
        })
        .catch(error => {
          console.log(error);
        });
    },
  },
};
</script>

后端代码（使用Koa）：

const Koa = require("koa");
const koaBody = require("koa-body");
const mysql = require("mysql");

const app = new Koa();
app.use(koaBody({ multipart: true }));

const db = mysql.createConnection({
  host: "localhost",
  user: "root",
  password: "password",
  database: "database_name",
});

app.use(async (ctx) => {
  if (ctx.url === "/upload" && ctx.method === "POST") {
    const file = ctx.request.files.image;
    const reader = fs.createReadStream(file.path);
    const filePath = path.join(__dirname, "uploads") + `/${file.name}`;
    const upStream = fs.createWriteStream(filePath);
    reader.pipe(upStream);

    db.query(
      `INSERT INTO images (name, path) VALUES (?, ?)`,
      [file.name, filePath],
      (error, results) => {
        if (error) {
          console.error(error);
          ctx.status = 500;
          ctx.body = "上传失败";
        } else {
          ctx.status = 200;
          ctx.body = "上传成功";
        }
      }
    );
  }
});

app.listen(3000, () => {
  console.log("Server is running on port 3000");
});

请注意，上述代码仅为示例，具体的数据库和文件存储配置需要根据实际情况进行修改。同时，需要安装相关依赖，如axios、koa、koa-body、mysql等。