Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
| Question 728 |
____key must satisfy referential integrity in a relation, while__key must satisfy entity integrity.
| Candidate, primary | |
| Foreign,primary | |
| Primary,foreign | |
| Foreign,superkey |
Question 728 Explanation:
→ To ensure entity integrity, it is required that every table have a primary key.
→ Neither the primary key nor any part of it can contain null values. This is because null values for the primary key mean we cannot identify some rows.
→ Referential integrity requires that a foreign key must have a matching primary key or it must be null. This constraint is specified between two tables (parent and child); it maintains the correspondence between rows in these tables. It means the reference from a row in one table to another table must be valid.
→ Neither the primary key nor any part of it can contain null values. This is because null values for the primary key mean we cannot identify some rows.
→ Referential integrity requires that a foreign key must have a matching primary key or it must be null. This constraint is specified between two tables (parent and child); it maintains the correspondence between rows in these tables. It means the reference from a row in one table to another table must be valid.
Correct Answer: B
Question 728 Explanation:
→ To ensure entity integrity, it is required that every table have a primary key.
→ Neither the primary key nor any part of it can contain null values. This is because null values for the primary key mean we cannot identify some rows.
→ Referential integrity requires that a foreign key must have a matching primary key or it must be null. This constraint is specified between two tables (parent and child); it maintains the correspondence between rows in these tables. It means the reference from a row in one table to another table must be valid.
→ Neither the primary key nor any part of it can contain null values. This is because null values for the primary key mean we cannot identify some rows.
→ Referential integrity requires that a foreign key must have a matching primary key or it must be null. This constraint is specified between two tables (parent and child); it maintains the correspondence between rows in these tables. It means the reference from a row in one table to another table must be valid.