Tadpole is a very easy to use SQL Client which allows users to connect and query various relational and non-relational databases right in a Web browser. No installation is required. Simply download Tadpole for Windows/Linux/Mac from its Github project, extract and launch it. Done! No special Web server or configuration is required. Most interesting of its features is that its ability to create or generate Entity-Relationship Diagrams. Check out this review blog for more info.