Q:

What language are SE Data Explorer queries written in?

I want to write a query for the Stack Exchange Data Explorer, but I'm not sure which language I need to learn in order to do so. At a glance it looks a bit like SQL, but I'm not entirely sure.
What language are SE Data Explorer queries written in?

A:

According to the Stack Exchange Data Explorer help page, queries are written in Transact-SQL.

A Quick Introduction to Data Explorer Queries
Click the Compose Query button up there and start typing your T-SQL
  query. That's it, it's really that easy! If you're not the
  query-writing type, you can still make use of all of the
  community-created queries, or check out the query tutorial for some
  help on how you can get started.

Thanks to animuson for pointing me towards the help page.

