Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
| Question 789 |
The primary key of any table is selected from the:
| Composite keys | |
| Foreign keys | |
| Candidate keys | |
| Alternate keys |
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.