I am pretty new to sql and i am trying to create a trigger that only starts, when a condition after an insert is met.

i have 3 columns. first column: productid, secound: productname, third: profit
i want to automate the insert. so when i insert 1 into the productid column, then i want the trigger to automaticly set productname to ‘protein powder’ and profit = 5$, but if i want insert 2 into productid column then i want to set productname = “creatine” and profit= 4$.
for that reason i need to use where or when. Everytime i use them it gives me an error.
does anyone have an idea how to fix that?

error code 1193. unkown system variable ‘productname’
and the where has a red underline

my code:

delimiter $$
create trigger productid1 # triggername = productid1

after insert on purchases # tablename is purchases

for each row

begin

set productname = “protein powder” and profit = 5; # productname and profit are columns

where productid = 1 # productid is the column where i want to insert the number into

end $$

delimiter ;