Compare rows in same table in mysql

Question

I have a mysql table like below

id   trader price
111  abc    5 
222  xyz    5.20 
333  abc    5.70 
444  xyz    5 
555  abc    5.20 

I nee

Answer 1

You will need to setup a separate table if you want to track a history of price changes. Also, when you refer to columns, it sounds like you mean rows.