SQL Foreign Key
1.What will be the output of below code?
CREATE TABLE dept (
dept_id INT PRIMARY KEY
);
CREATE TABLE emp (
emp_id INT,
dept_id INT,
FOREIGN KEY (dept_id) REFERENCES dept(dept_id)
);
INSERT INTO emp VALUES (101, 5);
-
A. Row inserted
-
B. Error: dept_id not found
-
C. dept_id auto-added
-
D. NULL inserted
Error: dept_id not found
Error: dept_id not found
2.What will happen?
INSERT INTO dept VALUES (10);
INSERT INTO emp VALUES (201, 10);
-
A. emp row inserted
-
B. Error
-
C. dept_id becomes NULL
-
D. Duplicate entry
emp row inserted
emp row inserted
3.What is the main role of a FOREIGN KEY?
-
A. Uniquely identify records
-
B. Link tables together
-
C. Create backups
-
D. Auto-update values
Link tables together
Link tables together
4.Which table contains the FOREIGN KEY?
-
A. Parent table
-
B. Reference table
-
C. Child table
-
D. Master table
Child table
Child table
5.Can a FOREIGN KEY reference a non-primary unique key?
-
A. Yes
-
B. No
Yes
Yes