SQL Developer + MySQL
By default, SQL developer can be used to connect only Oracle databases.

SQL Developer - Default Connection Option - Only Oracle Database
As you can see, there's only Oracle tab in the connection option. Luckily, SQL developer provides a very special feature that can import the third party JDBC driver into SQL developer. So that we can connect the third party databases other than Oracle's via this driver.
To connect MySQL databases from Oracle SQL Developer, we take the following steps to make SQL developer connect MySQL:
- Download MySQL JDBC driver from mysql.com.
- Open preference dialog in Tools's menu.
- Find "Third Party JDBC Driver".
- Add an Entry for MySQL JDBC driver.
- Check MySQL connections.
Download MySQL JDBC Driver
Before we import MySQL JDBC driver into SQL developer, we need to download it. Please go to MySQL :: Download Connector/J and look for a proper connector to download.
In the download page, please select Platform independent for your windows platform.
Please note that, in the compressed file, only one JAR file is useful. In my case, the file is called mysql-connector-java-8.0.14.jar. And I put it at the conventional path of JDBC library.

SQL Developer - jdbc - lib Content
Open Preference Dialog
Click on "Preference" function on "Tools" menu to open the dialog.

SQL Developer - Tools Menu
Find "Third Party JDBC Driver"
Expand "Database" and click on "Third Party JDBC Driver" in the preference dialog, then click Add Entry.

SQL Developer - Preference - Database - Third Party JDBC
Add an Entry for MySQL JDBC Driver
Select on our new driver file in the file selector to add the new JDBC driver.

SQL Developer - Preference - Database - Third Party JDBC - Select Path Entry
Now SQL developer has imported MySQL JDBC driver.

SQL Developer - Preference - Database - Third Party JDBC - MySQL Driver Added
Check MySQL Connections
Now, let's check the connection options again.

SQL Developer - Connection Options - MySQL Tab
As we can see, there's a new MySQL tab that offers capability to connect MySQL databases.
Now we can test the functionality of this MySQL JDBC driver by providing database information and credentials, then click Test.

SQL Developer - MySQL Connection Test - Status: Success
The test is successful. Which means the new driver is working now.
I got an error when i click “Test”:
Status : Failure -The server time zone value ‘WIB’ is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
Add in Port /?serverTimezone=UTC#
For example: 3306/?serverTimezone=UTC#
And test connection!
Regards
Thanks, this is a very clear set of instructions.
My pleasure!