Well, the first problem you'll run into is, which SQL implementation do you use? I think pretty much all discussion of the topic stops here since there are so many differences between the actual SQL standard and what the varios modern RDBMS' actually use.

The only real way past this hurdle is to create an intermediate SQL parser that uses your own interpretation of the standard, and at this point you may as well just use OData.

I'm not sure how valuable a discussion about just using the SQL implementation that comes with your RDMBS is, as doing this defeats all the effort we put into making our front ends ignorant of the underlying schema by locking the front-end into a specific SQL implementation for queries.