## Vertical fragmentation, Database Management System

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Vertical Fragmentation-Vertical fragmentation groups together only those attributes in a relation that are used jointly by various important transactions. A vertical fragment is described using the Projection operation of the relational algebra. In its most easy form, vertical fragmentation is the similar as that of decomposition. In common, a relation can be constructed on taking Natural join of all vertical fragments.

More usually, vertical fragmentation is accomplished by adding a special attribute known as a tuple-number to the scheme R. A tuple-number is a logical or physical address for a tuple. Therefore every tuple in R must have a unique address, the tuple- number attribute is a key to the new fragments get (please refer to Figure ).

 Branch-code Account number Customer name Balance Tuple-number 1101 3050 Suresh 5000 1 1101 2260 Swami 3360 2 1102 1170 Swami 2050 3 1102 4020 Khan 10000 4 1101 1550 Khan 620 5 1102 4080 Khan 1123 6 1102 6390 Khan 7500 7

Figure: The relation DEPOSIT of figure 5 with tuple- numbers

This  relation  now  can  be  decayed  into  two  fragments  as:  demonstrates  a  vertical decomposition of the scheme Deposit-scheme tuple number into:

DEPOSIT3 =  (branch-code. customer-name, tuple-number) (DEPOSIT)

DEPOSIT4 = ∏  (account-number, balance, tuple-number) (DEPOSIT)

The example of above Figure on this basis would become:

 DEPOSIT3 Branch-code Customer-name Tuple-number 1101 Suresh 1 1101 Swami 2 1102 Swami 3 1102 Khan 4 1101 Khan 5 1102 Khan 6 1102 Khan 7 DEPOSIT4 Account number Balance Tuple-number 3050 5000 1 2260 3360 2 1170 2050 3 4020 10000 4 1550 620 5 4080 1123 6 6390 7500 7

Figure: Vertical fragmentation of relation DEPOSIT

How can we rebuild the original relation from these 2 fragments? By taking natural join of the 2 vertical fragments on tuple-number. The tuple number permits direct retrieval of the tuples without the required for an index. Therefore, this natural join may be computed much extra efficiently than typical natural join.Though, please note that as the tuple numbers are system generated, thus they should not be visible to common users. If users are given access to tuple-number, it happens to impossible for the system to change tuple addresses.

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