moved subselects to "from" clause

[coreGreenberet]

just a small simplification on the estimated mileage calculation

instead of 4 subselects I've moved the tables to the "from" clause.

From:

SELECT
	convert_km((((SELECT odometer FROM last_position) - (SELECT odometer	FROM first_position)) /
	EXTRACT(days FROM (SELECT date FROM last_position) - (SELECT date	FROM first_position)) * 
	365)::numeric, '$length_unit') AS "mileage_$length_unit";

To:

SELECT
	convert_km(((lp.odometer - fp.odometer) /
	EXTRACT(days FROM lp.date - fp.date) * 
	365)::numeric, '$length_unit') AS "mileage_$length_unit" from first_position as fp, last_position as lp;

[adriankumpf]

Nice one!