hi,everyone,could you please help me for the below question?
and tell me why?
also,"NOT ENFORCED ENABLE QUERY OPTIMIZATION"
what does this statement mean?
thanks in advance
1)When defining a referential constraint, which delete rule will delete related rows in dependent tables when a row in the parent table is deleted?
b. Set null
d. No action
2)Given the following statements: CREATE TABLE students ( studentid integer NOT NULL, course char(4), CONSTRAINT courses CHECK ( course IN (‘MATH’, ‘CHEM’, ‘ENG1’, ‘HIST’)) NOT ENFORCED ENABLE QUERY OPTIMIZATION ) Which INSERT statement will NOT fail?
a. INSERT INTO students VALUES (11111, ‘MATH’)
b. INSERT INTO students VALUES (22222, MATH)
c. INSERT INTO students VALUES (‘22222’, ‘CHEM’)
d. INSERT INTO students VALUES (11111, ‘GEOG’)