we have the following table with no normal form
Num_orden Date client_num customer_dir Prod_no prod_desc Total_freedom total amount
--------------------------------- 1nf we remove the part that is repeated to know the corresponding record
to the each line of the order
orden_num (I keep the key of the original table) prod_no prod_desc unit price total amount (here this field is repeated in this table and the table that remains)
entity order line to apply 2nf ----------------------------------- 2nf we see that there is a partial dependence on the prod_desc and unit price of order_no Ask why? I see that for an order there are not several prod_no Is this the reason?
definition: Y functionally depends on X if and only if for each value of X there is one of Y
in any case the table that remains (if ord_num + prod_num is not chosen as the primary key) and it leaves ord_num serious:
ord_no prod_num total amount
and the entity prod
prod_no prod_desc and price_unit
but the first table would still maintain a dependency 1 to many of ord_num and prod_num (if you do not choose ord_num + prod_num) as the primary key. In other words, you would still be in partial dependence, would not you? and the condition for 2nf esque everything depends on the key of total form