Oracle - RETURNING combined with aggregate functions

Question

Oracle supports RETURNING clause which could be very useful.

For example for data:

CREATE TABLE t(Id INT, Val varchar2(50));

INSERT INTO t(         


        

Answer 1

The primary reason is that SQL is not composable. C. J. Date showed, at least in the 2009 class I attended in North Texas, that SQL is not composable. Because it's not composable, certain things don't come free. And by free, I mean without having even a thought. But the folks in Server Technologies are pretty smart and I'm sure the ones who managed the "add returning feature" project consciously determined where to draw the line. They apparently decided they would not "fully" write the parser. I suspect it's because they knew that if they took the position of 100% supportability, then as soon as some other part of SQL is enhanced, then they'd have to also spend time enhancing other parts of the language too.

I do admire ST for how fast their SQL parser executes and how rare it produces incorrect results. But I wonder, but not as fervently as Mr. Date, how much better the world might be if the dominant query language were at least composable.