A key:
A. must always be composed of two or more columns.
B. can only be one column.
C. identifies a row.
D. identifies a column.
Answer: Option C
Solution (By Examveda Team)
Option1: A key must always be composed of two or more columns because a composite key is used to uniquely identify a row in a table when a single column key is not sufficient.Option2: A key can only be one column is incorrect because a key can be composed of multiple columns to uniquely identify a row in a table.
Option3: A key identifies a row is correct. A key is used to uniquely identify a row in a table and ensure that each row is unique.
Option4: A key identifies a column is incorrect. A key is used to identify a row, not a column in a table.
In conclusion, the correct option is Option3: identifies a row. A key is used to uniquely identify a row in a table and ensure data integrity.
This Question Belongs to Database >> The Relational Model And Normalization
Related Questions on The Relational Model and Normalization
A. A → B.
B. A → C.
C. A → (B,C).
D. (B,C) → A.
A. normal forms.
B. referential integrity constraints.
C. functional dependencies.
D. None of the above is correct.
A relation is in this form if it is in BCNF and has no multivalued dependencies:
A. second normal form.
B. third normal form.
C. fourth normal form.
D. domain/key normal form.
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