|2003N 5 1ϊ||REPEATING GROUPS||BACK >> Ϊ|
@All files in RDB, Relational Data Base, should be represented as "flat files."@The "flat files" can be normalized by removing groups into separate tables, through the "First Normalization" in Codd's notation(*), as shown below:
@@oitem-NObitem-name, price-1, price-2, price-3p
@on the assumption that
@(1) The price-1 implies a fixed price (original price),
@So, we can get the normalized form as below:
@@ITEM: oitem-NObitem-namep [ R ]
The "repeating group" (of attributes) are said to be "polysemic" data in T-ERD.
The sign of "ER" on the right side of "ITEM. PRICE" tuple means "Entity. Role."
The "assortment-code" is newly required to assort the prices, such as with the value of "1" (in the assortment-code) for the original price, "2" for the discount price and "3" for the special price. So, you can identify the prices respectively.
The "assortment-code" is essentially different from the "partition-code".@The "partition-code" is the code for creating subsets, and the subsets can stand as data-clusters (in a set) at a time, although the prices cannot because the prices are "polysemic" data of an attribute.
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