Consider the following relation definition: STUDENT( Student_Number: integer NOT NULL Name: variable length character string length 20 NOT NULL) Primary Key Student_Number HOUSING( Housing_ID…

Consider the following relation definition:

STUDENT( Student_Number: integer NOT NULL Name: variable length character string length 20 NOT NULL) Primary Key Student_Number HOUSING( Housing_ID: integer NOT NULL Student_Number: integer NOT NULL Building: variable length character string length 25 NOT NULL) Primary Key Housing_ID Foreign Key Student_Number References STUDENT(Student_Number) ON DELETE NO CHECK ON UPDATE Which integrity constraint is violated in this relation definition?