Which two statements are true regarding constraints? (choose two.)
a. a foreign key cannot contain a null value.
b. a column with the unique constraint can contain null.
c. constraint is enforced only for the insert operation on a table.
d. constraints can be disabled even if the constraint column contains data
e. all the constraints can be defined at table as well as column level."?
Answers
Answer:
The correct answer is unique constraint column contains NULL and constraints will be disables if constraint column contains data.
Explanation:
Constraints are a query used in SQL. They are used for the purpose of limiting of the data type in a table. There are keys used in constraints such as primary keys and foreign keys.
The primary key cannot be a NULL and the foreign keys can become NULL.
There are six types of constraints namely:
1. Not NULL constraint
2. check constraint
3. Default constraint
4. Unique constraint
5. Primary constraint
6. Foreign constraint
Therefore, the constraints are used for the purpose of finding out the accuracy of data in the given database. It can also be in table level or column level.
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Answer:
The right answer is that if the unique constraint column contains NULL, constraints will be disabled, and if the constraint column includes data, constraints will be disabled.
Explanation:
Constraints are a query used in SQL. They are used for the purpose of limiting of the data type in a table. There are keys used in constraints such as primary keys and foreign keys.
The primary key cannot be a NULL and the foreign keys can become NULL.
There are six types of constraints namely:
1. Not NULL constraint
2. check constraint
3. Default constraint
4. Unique constraint
5. Primary constraint
6. Foreign constraint
As a result, the restrictions are employed in order to determine the accuracy of data in a specific database. It could also be at the table or column level.
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