Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
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Question 789
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The primary key of any table is selected from the:
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Composite keys
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Foreign keys
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Candidate keys
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Alternate keys
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Question 789 Explanation:
→ In the relational model of databases, a primary key is a specific choice of a minimal set of attributes (columns) that uniquely specify a tuple (row) in a relation (table).
→ Informally, a primary key is “which attributes identify a record”, and in simple cases are simply a single attribute: a unique id.
→ More formally, a primary key is a choice of candidate key (a minimal superkey); any other candidate key is an alternate key.
→ Informally, a primary key is “which attributes identify a record”, and in simple cases are simply a single attribute: a unique id.
→ More formally, a primary key is a choice of candidate key (a minimal superkey); any other candidate key is an alternate key.
Correct Answer: C
Question 789 Explanation:
→ In the relational model of databases, a primary key is a specific choice of a minimal set of attributes (columns) that uniquely specify a tuple (row) in a relation (table).
→ Informally, a primary key is “which attributes identify a record”, and in simple cases are simply a single attribute: a unique id.
→ More formally, a primary key is a choice of candidate key (a minimal superkey); any other candidate key is an alternate key.
→ Informally, a primary key is “which attributes identify a record”, and in simple cases are simply a single attribute: a unique id.
→ More formally, a primary key is a choice of candidate key (a minimal superkey); any other candidate key is an alternate key.