idea connect to database error Server returns invalid timezone. Need to set ‘serverTimezone’ property
the reason is that the default time zone in MySQL driver is UTC, which is eight hours different from local time (China), so the link cannot be connected.
click on Set time zone
1. Fill in GMT in the box and save! 
2. You can also add:?After the URL. serverTimezone=GMT
PS:
GMT (Greenwich Mean Time) : Greenwich Mean Time
UTC: world Standard Time
CST (China Standard Time) : China Standard Time
GMT + 8 = UTC + 8 = CST