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What is data model? Explain object based and record based data models?
Ans: A data model is an abstract model in which describes how data is represented and accessed.
(i) Object based data models: Same to a relational database model, but objects, classes and inheritance are directly supported within database schemas and in the query language
(ii) Record based data models: is a database model based on first-order predicate logic. Its core idea is to elaborate a database as a collection of predicates over a finite set of predicate variables, describing constraints on the possible values and combinations of values.
Define the terms i) Key attribute ii) Value set Key attribute: An entity type usually has an attribute whose values are exact from each individual entity in the collection. Su
How nulls are treated in comparison operator? Along with comparison (relational) operators, the null values are ignored as we cannot derive the relation along with the given op
database help
read-set(T) : Each data items that are read by a transaction T Timestamps : for all transaction T, the start-time and the end time are reserved for all the three phases.
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Explain the term- Query. Queries are used to repossess and show specific records in a table. They can also be used to show specific fields of specific records, which meet the co
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What are called jukebox systems? Jukebox systems have a few drives and numerous disks that can be loaded into single of the drives automatically.
Hashed File Organisation Hashing is the most common form of purely random access to a database or file. It is also used to access columns that do not have an index as an optimi
Question 1: a) What is the difference between a non-impact and impact printer? b) Which type of printer is generally used in a supermarket to print your receipt? Describe
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