database

Common database errors across PostgreSQL, MySQL, MongoDB, Redis, and SQLite.

Skills
Development
288

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Content

# Database Error Patterns

Common database errors across PostgreSQL, MySQL, MongoDB, Redis, and SQLite.

## Connection Errors

### Connection Refused

```
Error: connect ECONNREFUSED 127.0.0.1:5432
FATAL: connection refused
```

**Causes**:
1. Database server not running
2. Wrong host/port
3. Firewall blocking connection
4. Max connections reached

**Diagnosis**:
```bash
# Check if database is running
# PostgreSQL
pg_isready -h localhost -p 5432

# MySQL
mysqladmin ping -h localhost

# Check port
lsof -i :5432
netstat -an | grep 5432

# Check process
ps aux | grep postgres
ps aux | grep mysql


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