For the cost of a single table scan, you may be better with:
select max(foo) - min(foo) where etc.
S.
--
Anyone using floating point for financial computations needs their head
examined.
On 12/20/18 4:32 PM, Jens Alfke wrote:
On Dec 20, 2018, at 4:21 PM, Jungle Boogie <jungleboog...@gmail.com> wrote:
select od_reading from mileage where car='foo' limit 1
select od_reading from mileage where car='bar' order by od_reading desc limit 1
Note: the first query should use “order by od_reading”, otherwise the order is
undefined.
A clearer way to specify these is
select min(od_reading) from mileage where car=‘foo’
select max(od_reading) from mileage where car=‘foo’
How do I subtract the last query from the first query to determine how many
miles were driven?
It’s super simple:
(select od_reading from mileage where car='foo' limit 1) - (select od_reading
from mileage where car='bar' order by od_reading desc limit 1)
—Jens
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