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What are the problems if one were not to normalize? When do these problems surface?
Ans: Database normalization, sometimes considered to as canonical synthesis, is a method for designing relational database tables to minimize duplication of information and, in so doing, to preserve the database against specific types of logical or structural problems, that are data anomalies. For instance, when multiple instances of a given piece of information take place in a table, the possibility exists that these examples will not be kept consistent while the data within the table is updated, leading to a loss of data integrity. A table that is adequately normalized is less vulnerable to problems of this type, as its structure reflects the basic assumptions for while multiple instances of similar information should be denoted by a single instance only.
Define outer union operation of the relational algebra. Compute the outer union for the relations R and S given below. Outer Join - If there are any values in one tabl
Fourth Normal Form (4NF) When attributes in a relation have multi-valued dependency, further Normalization to 4NF and 5NF are needed. Let us first find out what multi-valued d
Consider the following relations: BRANCH( bno, street, area, city, pcode, Tel_no, Fax_no) STAFF( Sno, Fname, Lname, address, position , salary, bno) Express the subsequent qu
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
Explain data independence ? Data independence is the capacity to modify the schema at one stage of a database system without having to change the schema at the further level.
How does a query tree represent a relational algebra expression? Discuss any three rules for query optimisation, giving example as to when should each rule be applied. Ans
Lossless-Join Decomposition Let us show an intuitive decomposition of a relation. We require a better basis for deciding decompositions since intuition may not always be r
construct an er diagram for a hospital with a set of patients and a set of medical doctors. associate with each patient a log of various test and examination conducted.convert er d
Explain the main advantages of DBMS over File Oriented System ?
intent locking
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