If you were on server, it's quite simply standard SQL - "MySQL" is SQL, as is Oracle SQL, PostGreSQL, MS-SQL and the others. (Yes, some of the usage varies, like line endings, cases, server commands etc, but the definition of SQL does not include them. "Select * from X where Y" works across all SQL based databases)
But you said Cloud, so you can forget it. You have no access to the underlying database on Cloud, you'll need to work over the REST API. That only allows the use of JQL, not SQL.
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events