Sql Interview Question and Answers

81. What is De-normalization?
  De-normalization is the process of attempting to optimize the performance of a database by adding redundant data.
De-normalization is a technique to move from higher to lower normal forms of database modeling in order to speed up database access.
 
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82. What is referential integrity?
  Referential integrity refers to the consistency that must be maintained between primary and foreign keys, i.e. every foreign key value must have a corresponding primary key value.
 
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83. What is the difference between static and dynamic SQL?
  Static SQL is hard-coded in a program when the programmer knows the statements to be executed.
For dynamic SQL the program must dynamically allocate memory to receive the query results.
 
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84. Define Unique Key?
  Unique key is a one or more column that must be unique for each row of the table.
It is similar to primary key. Primary key column will not accept a null. Whereas the unique key column will accept a null values.
 
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85. Define Synonym?
  Synonym is an alternative method to creating a view that includes the entire table or view from another user it to create a synonym.
A synonym is a name assigned to a table or view that may thereafter be used to refer to it.
 
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