Computer Science Ques 491

Question: Which of the following types of tables constraints will prevent the entry of duplicate rows?

Options:

A) Primary key

B) Unique

C) Null

D) foreign key

E) None of these

Show Answer

Answer:

Correct Answer: A

Solution:

  • The primary key of a relation-al table uniquely identifies each record or row in the table. For a table. It enables each record to be unique without ambiguity that is. it doesn’t allow duplicate’s, eg, In a table CUSTOMERS, ii is difficult to differentiate each on his name. Since homonyms may ex its. Therefore, it creates a field Code Client where each code is unique in designating it as primary key to ensure that every client is different.
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