LINQPad can be used for LINQ queries, but also for any C#/F#/VB expression, statement block or program.
Includes drivers for SQL Server, SQL Azure, SQL CE, Oracle, SQLite, MySQL etc.
Ranked in these QuestionsQuestion Ranking
Pro The ideal coding scratch pad
Pro Dark theme
Can be deployed portable all files are optional apart from LINQPad.exe and LINQPad.exe.config.
Con PostgreSQL driver
PostgreSQL support is not included, but a driver can downloaded from GitHub.
Con Windows only
But LINQ Pad 6 will support .Net Core 3.0.