MapReduce in terms of SQL

I found a great explanation of MapReduce in terms of SQL in a blog post about Hadoop by Chris Stucchio:

SQL-ish pseudocode:

SELECT G(...) FROM table GROUP BY F(...)

[…]

The only thing you are permitted to touch is F(k,v) and G(k,v), except of course for performance optimizations (usually not the fun kind!) at intermediate steps. Everything else is fixed.