Useful online sites/services

SQL Fiddles

It happens that we want to test sql on a particular db, and do not have it installed.
There are sites which provide us a testing environment for various databases. e.g.
Note that some sites may consider whatever you submit to be under commons creative license.

https://dbfiddle.uk/ ( This one has mariadb too )
http://www.sqlfiddle.com/#!3/e48975/1