* postgresql >= 12

* `PostgreSQL` >= 12
    * [`first_last_agg`](https://github.com/wulczer/first_last_agg)
	    * `LLVM` >= 8
		* `Clang` >= 8

## first_last_agg installation if package not available
```
git clone https://github.com/wulczer/first_last_agg.git
cd first_last_agg
#apt-get install postgresql-server-dev-12 build-essential
make install #sudo if not root
```

create extension if not exists first_last_agg;
-- Create a function that always returns the first non-NULL item
create function public.first_agg (anyelement, anyelement)
returns anyelement language sql immutable strict as $$
	select $1;
$$;
 
-- and then wrap an aggregate around it
create aggregate public.first (
	sfunc    = public.first_agg,
	basetype = anyelement,
	stype    = anyelement
);
 
-- create a function that always returns the last non-null item
create function public.last_agg (anyelement, anyelement)
returns anyelement language sql immutable strict as $$
	select $2;
$$;
 
-- and then wrap an aggregate around it
create aggregate public.last (
	sfunc    = public.last_agg,
	basetype = anyelement,
	stype    = anyelement
);

							min_price

							min_price,
							q

									min(price) as min_price

									min(price) as min_price,
									first(quantity) as q