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Explain the concept of a data model ?
Data Model - Model is an abstraction procedure which hides irrelevant details although highlighting details relevant to the applications at hand. As same, a data model is a collection of concepts which can be used to elaborate structure of a database and gives the essential means to achieve this abstraction. Structure of database means the data types, relationships, and constraints which should hold for the data. In common a data model consists of two elements:
• A mathematical notation for expressing relationships and data.• Operations on the data which serve to express queries and other manipulations of the data.
What subschema expresses ? A subschema expresses the external view. (External schemas are called also called as subschemas)
Explain Candidate key? Candidate Key - A candidate key is a minimal superkey, that can be used to uniquely identify a tuple in the relation.
What are the comparison operator in SQL? Comparison operator in SQL are =, LIKE and BETWEEN
What is the difference between internal tables and extract datasets? The lines of an internal table always have the similar structure. By using extract datasets, you can ha
User error : This contains errors in the program (e.g., Logical errors) with errors made by online users of database. These types of errors can be avoided by applying some check
What is a value? A data value is used for identity. This form of identity is used in relational systems.eg: The primary key value of a tuple recognize the tuple.
Explain mechanism of nested queries? SQL gives a mechanism for nesting subqueries. A subquery is a select from where expression that is nested within one more query. A common u
Question: (a) e-Government implementations normally evolve through a multi-stage process. Describe, using appropriate examples, the stages involved in an e-Government implemen
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what is file organization? what are file organization techniques.explain in detail? explain random file organization technique, multikey file organization technique?what is indexin
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