How to correctly compose a condition in MYSQL (example inside)?

Question

PHP

I need to output data by comparing 2 cells in the same table. For example price and old_price, output if price is less than old_price

Answer 1

SELECT price, old_price FROM table WHERE price < old_price

Answer 2

select case 
when price < old_price then price 
when old_price < price then old_price 
end as final_price