join - How to make this SQL SELECT? -

i cant figure out how make comparison select both years every plant.

select plantname, sum(amount) amount_harvested_2014  harvest year=2014 group plantname 

in desired output row should this:

plantname  2014amount  2015amount  2015-2014amount 

the table:

create table harvest(  harvest_id int primary key identity(1,1),  plantname nvarchar(20) not null foreign key references plants(plantname),  amount int not null,  year int,  harvester_id int not null foreign key references workers(worker_id) ) 

and example content of table:

harvest_id  plantname   amount  year    harvester_id 1           rose        32      2015    2 2           rose        12      2015    5 

one simple way (which might not best) use conditional aggregation this:

select      plantname     ,sum(case when year=2014 amount else 0 end) "2014amount"     ,sum(case when year=2015 amount else 0 end) "2015amount"     ,sum(case when year=2015 amount else 0 end) - sum(case when year=2014 amount else 0 end) "2015-2014amount" harvest group plantname