SQL Developer - Oracle SQL Developer is a free, development environment that simplifies the management of Oracle Database in both traditional and Cloud deployments.
draw.io - Online diagramming application
phpMyAdmin - phpMyAdmin is a tool written in PHP intended to handle the administration of MySQL over the Web.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
DBeaver - DBeaver - Universal Database Manager and SQL Client.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.