Sql Interview Question and Answers

121. What is a data model?
  It is a collection of concepts that can be used to describe the structure of a database. It provides necessary means to achieve this abstraction. By structure of a database we mean the data types, relations, and constraints that should hold on the data.
 
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122. What are types of schema?
 
  • Internal schema
  • Conceptual schema
  • External schema
 
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123. What are different types of DBMS?
 
  • DBMS
  • RDBMS (Relational)
  • ORDBMS (Object Relational)
  • DDBMS (Distributed)
  • FDBMS (Federated)
  • FDBMS (Federated)
  • HDBMS (Hierarchical)
  • NDBMS (Networked)
 
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124. What is a lock?
  A lock is a variable associated with a data item that describes the status of the item with respect to the possible operations that can be applied to it.
 
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125. What are the purpose of Normalisation?
 
  • Minimize redundancy in data.
  • Remove insert, delete and update anamoly during the database activities.
  • Reduce the need to reorganize data it is modified or enhanced.
 
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