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Insulation between conceptual and physical structures
It can be defined as:
1. The Database Administrator should be capable to vary the storage structures without affecting users' views.
2. The internal structure of the database should be unaffected by the varies to the physical aspects of the storage, like changing to a new storage device.
3. The DBA should be able to vary the conceptual structure of the database without affecting all users.
Example :; transfers transfer_amount from x's account to y's account ; Supposes x&y both accounts exist TRANSACTION (x, y, transfer_amount) Start transaction IF X AND Y
Nested Queries Let us see some more complex queries in this section. Sub-queries: Some of the basic concerns of sub-queries are: A sub-query is a SELECT statemen
What is a cascading update? Referential integrity constraints needs that foreign key values in one table correspond to primary key values in another. If the value of the primar
(a) Provide the description of the following ODMG schema in the Object Definition Language (ODL). (b) Based on the above object database, write the following queries i
tell me the functionality,advantages and disadvantages of student database
Unrepeatable reads : Assume T7 reads X twice during its implementation. If it did not update X itself it could be very disturbing to see a dissimilar value of X in its next read. B
In which format database schema is written ? Data base schema is written in the DDL format.
Consider an information system designed for an online company which provides IT products and services These include desktops, laptops, networking products, IT books, parts, and
Which data manipulation command combines the records from one or more tables ? JOIN data manipulation command combines the records from one or more tables.
What are wait-for-graphs?Give the algorithm to construct a wait-for-graph from a given schedule of transactions? How can deadlocks be detected from wait-for-graphs? Ans: The
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