# Solving SQL Connectivity Issues in Docker: A Step-by-Step Guide

## **The Problem: MySQL Connection Errors in Docker**

While setting up my [Expense Tracker WebApp](https://github.com/DevNishantHub/Expenses-Tracker-WebApp) with **Spring Boot + MySQL** using Docker, I encountered persistent SQL connectivity issues. My `docker-compose.yml` file looked correct, but the application failed to connect to the MySQL container with errors like:

* `Communications link failure`
    
* `Access denied for user 'root'`
    
* `Unknown database 'expenses_tracker'`
    

## **The Solution: Clean Reinstallation of MySQL Docker Containers**

After several frustrating hours, I discovered that **lingering Docker volumes and old MySQL images** were causing conflicts. Here's how I fixed it:

### **Step 1: Stop and Remove Existing Containers**

bash

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```plaintext
docker-compose down
```

### **Step 2: Delete Old MySQL Volumes (Backup First!)**

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```plaintext
docker volume ls  # Identify volumes
docker volume rm <volume-name>  # Remove the conflicting ones
```

**⚠️ Warning:** This deletes your database data. Backup first if needed!

### **Step 3: Pull a Fresh MySQL Image**

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```plaintext
docker pull mysql:8.0
```

### **Step 4: Recreate Containers**

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```plaintext
docker-compose up --build
```

## **Key Takeaways**

1. **Docker volumes persist** even after container removal, which can cause conflicts
    
2. **Authentication plugin changes** in MySQL 8+ can break existing setups
    
3. **Clean installation** is often faster than debugging obscure connection issues
    

You can check out my complete implementation in the [Expense Tracker GitHub repo](https://github.com/DevNishantHub/Expenses-Tracker-WebApp). Connect with me on [LinkedIn](https://www.linkedin.com/in/nishant-kumar-b8aa6b313/) to discuss more Docker tips!