create table s
(s# char(4),
sname char (8) not null,
age smallint,
sex char(1),
primary key(s#))create table c
(c# char(4),
cname char(10),
teacher char(8),
primary key(c#))create table sc
(s# char(4),
c# char(4),
grade smallint,
primary key(s#,c#),
foreign key(s#) references s(s#),
foreign key(c#) references c(c#),
check ((grade is NULL) OR (grade between 0 and 100)))
(s# char(4),
sname char (8) not null,
age smallint,
sex char(1),
primary key(s#))create table c
(c# char(4),
cname char(10),
teacher char(8),
primary key(c#))create table sc
(s# char(4),
c# char(4),
grade smallint,
primary key(s#,c#),
foreign key(s#) references s(s#),
foreign key(c#) references c(c#),
check ((grade is NULL) OR (grade between 0 and 100)))
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