Consider a database storing the data of invoices, and each invoice takes the following form:

Invoice_Num: 1480
Handled By: John Keaton
Staff Num: 263
Staff Position: Trainee

Item_Num    Item_Desc         Unit_Price   Qty
========    ==============    ==========   ===
 15003      Blue Ballpen         2.00       5
 15012      5ml Gluestick        0.80       3

Assumptions:

• Each invoice is handled by 1 and only 1 staff.
• Each item in the same invoice is unique.

So, in 1NF, the data can be represented as:

Invoice [ Invoice_Num, Staff_Num, Staff_Name, Staff_Pos, Item_Num, Item_Desc, Unit_Price, Qty ]

where Invoice_Num and Item_Num form the primary key.

Now we know that Invoice_Num -> Staff_Num, and Staff_Num -> Staff_Pos, and Staff_Num -> Staff_Name.

But then when the database is normalized to 2NF, should we move the Staff_Pos and Staff_Name to another table? If we use the transitive property, we have Invoice_Num -> Staff_Pos, and Invoice_Num -> Staff_Name, then we should move them to another table to eliminate partial dependency. However, with the use of transitive property, should these 2 dependencies be considered transitive dependency instead, and hence moving Staff_Pos and Staff_Name to another table should be done in 3NF?