Correct SQL Create Table Statement? - sql

Question

I've been stuck on this final table/data dictionary that I'm working on and I'm not quite sure on the syntax of the create table statement.
Data Dictionary:
TABLE NAME: Enrollment
Sid (Column Name)
NUMBER(Data Type)
5(Length)
blank(not null)
Y(PK)
Y(FK)
Blank(Check)
Csecid(Column Name)
NUMBER(Data Type)
8(Length)
blank(not null)
Y(PK)
Y(FK)
Blank(Check)
Grade(Column Name)
CHAR(Data Type)
1(Length)
blank(not null)
Blank(PK)
Blank(FK)
A,B,D,D,F,I,W(Checks).
Notes:
Sid is also defined as the PK on the STUDENT table.
Csecid is also defined as the PK on the COURSE_SECTION table.
I don't know how to define both Sid and Csecid in the Create table statement as both PK and FK. Please help. Thanks!

Answer 1

In my understanding you need to create a mapping table Enrollment for tables Student and Course_Section, because Student and Course_Section have many-to-many relationship.
Following lists the sample schema and create table queries:
-- Create Student Table
create table student(sid number(5) primary key, sname varchar2(100),
dob date);
-- Insert some data
insert into student values(1,'student1','01-feb-1990');
insert into student values(2,'student2','01-mar-1990');
insert into student values(3,'student3','01-apr-1990');
insert into student values(4,'student4','01-may-1990');
commit;
-- Create Course_Section Table
create table course_section(csecid number(8) primary key,
csname varchar2(30));
-- Insert some data
insert into course_section values(115,'CS1');
insert into course_section values(116,'CS2');
insert into course_section values(117,'CS3');
insert into course_section values(118,'CS4');
insert into course_section values(119,'CS5');
commit;
-- Since student and course_section have many-to-many relationship
-- One student can enroll to many courses
-- One course can be associated with many students
-- They need to be related using separate table
create table enrollment(sid number(5) not null,
csecid number(8) not null,
grade char(1) not null,
constraint e_pk primary key(sid, csecid),
foreign key (sid) references student(sid),
foreign key (csecid) references course_section(csecid),
constraint gc_constraint check (grade in ('A','B','C','D','F','I','W')));
-- Insert some records in enrollment
insert into enrollment values(1,115,'D');
insert into enrollment values(2,118,'C');
insert into enrollment values(1,118,'C');
insert into enrollment values(2,117,'A');
insert into enrollment values(4,116,'B');
insert into enrollment values(3,118,'I');
insert into enrollment values(4,118,'W');
commit;
Check this sqlfiddle to know more.