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Explain Data Sublangauges ?
Data sublanguage: In relational database theory, the term sublanguage, first used for this purpose through E. F. Codd in the year of 1970, refers to a computer language used to describe or manipulate the structure and contents of a relational database management system (RDBMS). Typical sublanguages related along with modern RDBMS's are QBE (Query by Example) and SQL (Structured Query Language).
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
Define the five basic operators of relational algebra? Five basic operators of relational algebra are: 1. Union (∪∪∪∪) - Selects tuples which are in either P or Q or in both
Un-Normalized Form (UNF) If a table having non-atomic values at every row, it is said to be in UNF. An atomic value is something that cannot be further decomposed. A non-atomic
Performance of Various Concurrency Control Mechanisms
Question: One of the tasks a database management system must perform is to ensure that the data is still intact in the face of software and hardware failure. This task is known
What are aggregate functions? And list the aggregate functions supported by SQL? Aggregate functions are functions that take a collection of values as input and return a one va
Higher Normal Forms Is there more normal forms beyond BCNF? Yes, though, these normal forms are not based on the concept of functional dependence. More normalisation is needed if
What is substitutability? Any method of a class-say A can equally well be adjured with any object belonging to any subclasses B of A. This characteristic leads to code reuse, a
What is document scanning and imaging? Document scanning and imaging, or digital archiving, is the method of scanning a document into a digital image to archive and retrieve a
What is OCR? OCR (Optical Character Recognition) is a technology that enables you to change different types of machine-readable documents, like scanned paper documents, PDF fil
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