Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
| Question 720 |
Referential integrity constraints works on the concept of:
| Secondary key
| |
| Super key
| |
| Foreign key
| |
| Primary key
|
Question 720 Explanation:
Referential integrity constraints works on the concept of foreign key.
Referential Integrity Rules
→ A referential integrity rule is a rule defined on a key (a column or set of columns) in one table that guarantees that the values in that key match the values in a key in a related table (the referenced value).
→ Referential integrity also includes the rules that dictate what types of data manipulation are allowed on referenced values and how these actions affect dependent values.
The rules associated with referential integrity are:
1. Restrict: Disallows the update or deletion of referenced data.
2. Set to Null: When referenced data is updated or deleted, all associated dependent data is set to NULL.
3. Set to Default: When referenced data is updated or deleted, all associated dependent data is set to a default value.
4. Cascade: When referenced data is updated, all associated dependent data is correspondingly updated. When a referenced row is deleted, all associated dependent rows are deleted.
5. No Action: Disallows the update or deletion of referenced data. This differs from RESTRICT in that it is checked at the end of the statement, or at the end of the transaction if the constraint is deferred.
Referential Integrity Rules
→ A referential integrity rule is a rule defined on a key (a column or set of columns) in one table that guarantees that the values in that key match the values in a key in a related table (the referenced value).
→ Referential integrity also includes the rules that dictate what types of data manipulation are allowed on referenced values and how these actions affect dependent values.
The rules associated with referential integrity are:
1. Restrict: Disallows the update or deletion of referenced data.
2. Set to Null: When referenced data is updated or deleted, all associated dependent data is set to NULL.
3. Set to Default: When referenced data is updated or deleted, all associated dependent data is set to a default value.
4. Cascade: When referenced data is updated, all associated dependent data is correspondingly updated. When a referenced row is deleted, all associated dependent rows are deleted.
5. No Action: Disallows the update or deletion of referenced data. This differs from RESTRICT in that it is checked at the end of the statement, or at the end of the transaction if the constraint is deferred.
Correct Answer: C
Question 720 Explanation:
Referential integrity constraints works on the concept of foreign key.
Referential Integrity Rules
→ A referential integrity rule is a rule defined on a key (a column or set of columns) in one table that guarantees that the values in that key match the values in a key in a related table (the referenced value).
→ Referential integrity also includes the rules that dictate what types of data manipulation are allowed on referenced values and how these actions affect dependent values.
The rules associated with referential integrity are:
1. Restrict: Disallows the update or deletion of referenced data.
2. Set to Null: When referenced data is updated or deleted, all associated dependent data is set to NULL.
3. Set to Default: When referenced data is updated or deleted, all associated dependent data is set to a default value.
4. Cascade: When referenced data is updated, all associated dependent data is correspondingly updated. When a referenced row is deleted, all associated dependent rows are deleted.
5. No Action: Disallows the update or deletion of referenced data. This differs from RESTRICT in that it is checked at the end of the statement, or at the end of the transaction if the constraint is deferred.
Referential Integrity Rules
→ A referential integrity rule is a rule defined on a key (a column or set of columns) in one table that guarantees that the values in that key match the values in a key in a related table (the referenced value).
→ Referential integrity also includes the rules that dictate what types of data manipulation are allowed on referenced values and how these actions affect dependent values.
The rules associated with referential integrity are:
1. Restrict: Disallows the update or deletion of referenced data.
2. Set to Null: When referenced data is updated or deleted, all associated dependent data is set to NULL.
3. Set to Default: When referenced data is updated or deleted, all associated dependent data is set to a default value.
4. Cascade: When referenced data is updated, all associated dependent data is correspondingly updated. When a referenced row is deleted, all associated dependent rows are deleted.
5. No Action: Disallows the update or deletion of referenced data. This differs from RESTRICT in that it is checked at the end of the statement, or at the end of the transaction if the constraint is deferred.
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