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A Relation Schema represented by R(A1, A2, ..., An) is made up of the relation name the list of attributes and R Ai that it contains. A relation is described as a set of tuples. Let r be the relation which have set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).
The purpose of the relational model is to give a declarative function for specifying queries and data: users directly state what information the database have and what information they want from it, and let the database management system software take care of explain data structures for retrieval procedures and storing the data for answering queries.
Selective replication: This is a combination of generating small fragments of relation and replicating them rather than a entire relation. The data should be fragmented on require
Support by Adding Indexes Multiple indexes can be used to access a data file by multiple access paths. In such a scheme only single copy of the data is consider, only the numbe
Consider the table student and list names of students in the departments other than maths and computer. SELECT std_name FRM student WHERE dept_name NOT IN (‘Maths','Computer);
The Database Approach In order to overcome the limits of a file system, a new approach was needed. Hence a database approach emerged. A database is a persistent collection of
Multiple-mode locks : It offers two locks: exclusive locks and shared locks. But why do we require these two locks? There are a lot of transactions in the database system that neve
Define instance and schema? Instance: Collection of data stored in the data base at a certain moment is Schema: The overall design of the data base is known as the data base
What is multiplicity in the associations? Give an example to explain multiplicity? Multiplicity in association indicate number of objects participate in any relationship. For
If R1 and R2 are two relations or functions, then the result of R3 = R1 × R2 is the combination of tuples that are in R1 and R2. The product is associative and commutative. Degr
construct a B+ tree for the following set of key value (2,3,5,7,11,19,23,29,31) in ascending order where the pointers that will fit in one node is as follows:A. four B. six C. eigh
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