MySQL 1170: Cannot open database.

  1. Check if the MySQL service is running:


- On Linux, run: `sudo systemctl status mysql`
- On Windows, open Services and look for MySQL service.

  1. Verify MySQL server is reachable:


- Run: `mysql -h [hostname] -u [username] -p`

  1. Check database existence:


- Connect to MySQL: `mysql -u [username] -p`
- List databases: `SHOW DATABASES;`
- Ensure the targeted database is listed.

  1. Examine user privileges:


- After connecting to MySQL: `SHOW GRANTS FOR 'youruser'@'yourhost';`

  1. Review error logs for specific error messages:


- Default location on Linux: `/var/log/mysql/error.log`
- On Windows, located in MySQL installation directory, `data` folder.

  1. Check for disk space:


- On Linux: `df -h`
- On Windows: Open This PC and check the disk where MySQL is installed.

  1. Assess MySQL server status and variables:


- Connect to MySQL and run: `SHOW STATUS LIKE 'uptime';` to check if the server is running.
- Check open connections: `SHOW STATUS LIKE 'Threads_connected';`

  1. Repair database in case of corruption (if the database is marked as crashed or corrupted):


- Connect to MySQL and run: `REPAIR TABLE tablename;` for the specific table(s) reported in errors, or
- Use myisamchk for MyISAM tables if the server is stopped: `myisamchk --recover /path/to/table.MYI`

  1. Increase connection limits if too many connections:


- Check max connections: `SHOW VARIABLES LIKE 'max_connections';`
- Temporarily increase: `SET GLOBAL max_connections = [higher number];`

  1. Restart MySQL Service:


- On Linux: `sudo systemctl restart mysql`
- On Windows: Restart the MySQL service from Services.

Perform these actions in sequence, checking after each step if the error persists before proceeding to the next.

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