Ginger Grant has a quick intro on U-SQL:
In my previous series on Stream Analytics, I wrote some U-SQL. That U-SQL didn’t look much different than Ansi-SQL, which is sort of the point of porting the functionality to a different yet familiar language. Another application which heavily uses U-SQL is Azure Data Lake. Data Lake stores its data in HDInsight, but you don’t need to write hive to query the data, as U-SQL will do it. Like Hive, U-SQL can be used to create a schema on top of some data, and then query it.
For example, to write a query on this csv file stored in a Data Lake, I would need to create the data definition for the data, then I could easily write a statement to query it.
I’m interested in seeing how much adoption we see in this language.