MySQL Update Procedure

a. If the selling price is lower than the average, the 10% selling price

b. If the selling price is higher than the average it increases by 5%

The procedure has to receive the co-product of the products.

Show a table with the following columns on the screen: codigoproducto, precioventa before updating and precioventa after update it.

I have tried it in this way but the Price displayed is 0 ... Any idea how to do it? Thank you very much in advance.

drop procedure if exists procedimiento1;

DELIMITER //

create procedure procedimiento1 (in codproducto int(5))

begin

update productos 
    set PrecioVenta= case 
        when PrecioVenta<(select avg(PrecioVenta)) then PrecioVenta+(PrecioVenta*0.10)
        when PrecioVenta>(select avg(PrecioVenta)) then PrecioVenta+(PrecioVenta*0.05)
    end
    where CodigoProducto=codproducto;

select CodigoProducto, PrecioVenta from productos where CodigoProducto=codproducto;

end//

DELIMITER //

call procedimiento1 (11679);