Build a backend service or middleware using Node.js, PHP, Python, or whatever language you like. This will act as a bridge between Adalo and your MySQL database.

Here's an example in Node.js using Express and the mysql package:
```javascript
const express = require('express');
const mysql = require('mysql');
const app = express();

const db = mysql.createConnection({
host: 'your-db-host',
user: 'your-db-username',
password: 'your-db-password',
database: 'your-database-name'
});

db.connect(err => {
if (err) throw err;
console.log('Connected to database');
});

app.use(express.json());

app.get('/get-data', (req, res) => {
const sqlQuery = 'SELECT * FROM your_table';
db.query(sqlQuery, (err, results) => {
if (err) throw err;
res.json(results);
});
});

const PORT = process.env.PORT || 5000;
app.listen(PORT, () => console.log(Server running on port ${PORT}));
```