2020.11.19 1. (20 points) Suppose that one database includes four relations, teaches relation T(Tno, Tname. Title. ID Card), with attributes teacher number Ino), teacher namelirane) professional Tile(Title) and IdCard Number(ID Card); relation C(cro. Crame, Tno), with attributes the course number(Cro), course name(Crame) and teacher number of this course(Tno);student relation S(Sno, Firstname, Lastname, Birthday, Sex,ID Card) with Student number(Sno). name . birthday and gender and IdCard Number(ID Card); course selection relation SC(Sno, Cno, Score) with attributes the student number(Sno), course number(Cho) and Score. Accoring to the common situations in the real world: (each 4 points) (1) Please give two reasonable candidate keys, one primary key for teacher relation. Tno, ID Card (2) Write the primary key and a foreign key of SC relation, then exlain the meaning of them respectively. primary key Sno, Cno foreign key:Sno, its value references the value for attribute sno in student relation. (3) Give suitable datatype for attribute Birthday in S relation and Score in relation SC? Datetime float (4) Add constraint with values beween 0 and 100 for attribute Score in SC realtion. Check(score between 0 and 100) (5) Add constraint "Not Null" for Title in relation T. Alter table T add constraint title not null