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Explain Derived and Non-Derived Attribute?
In few cases, two or more attribute values are related, for instance, Age and BirthDate attributes of a person. For specific person entity, the value of Age can be determined from the current date and the value of that person's BirthDate. Therefore, the attribute Age is known as derived attribute and the attribute BirthDate is known as non-derived or stored attribute.
I am doing research in this area, especially in sime join and join efficacy when several relations have been queried. Relations located in different sites. I need something like n
The First Normal Form (1NF) Let us first describe 1NF: Definition: A relation (table) is in 1NF if 1. There are no duplicate tuples or rows in the relation. 2.
Association as a cache This association must be updated when any new element is added to it, but testing for overlap using association is more efficient. Figure:
we need example of 2phase locking
Find the names of all Albums that have more than 30 tracks. Result: (name: varchar(255))
Explain the structure of well formed formulae in relational calculus. Ans: a. An atom is a formula b. If P1 is a formula, after that so are ¬P1 and (P1) c. If P1 and P2 a
Strong entity set and weak entity set? Strong entity set and weak entity set: A strong entity set has a primary key. All tuples in the set are distinguishable through that key.
Briefly describe concurrency execution? Lock - based protocols Locks There are several modes in which a data item may be locked in this section we restrict our attention
Describe Hashing in DBMS? Hashing: Hashing is a technique to store data within an array so which storing, searching, inserting and deleting data is fast (in theory it's O(1))
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
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