SPJデータベース-最初にSQLステートメントに精通している（2）

create table s
(sno char(4) primary key,
 sname char(20),
 status char(4),
 city char(20)
 )
 
 create table p
 (pno char(4) primary key,
  pname char(20),
  color char(6),
  weight smallint
 )
 
 create table j
 (jno char(4) primary key,
  jname char(20),
  city char(20)
 )
 
 create table spj
 (sno char(4) references s(sno),
  pno char(4) references p(pno),
  jno char(4) references j(jno),
  qty smallint,
  primary key(sno,pno,jno)
 )

/*
create table spj
(sno char(4),
 pno char(4),
 jno char(4), 
 qty smallint,
 primary key(sno,pno,jno),
 foreign key (sno) references s(sno),
 foreign key (pno) references p(pno),
 foreign key (jno) references j(jno)
 )
*/

select distinct sno
from spj
where jno='j1'

select distinct sno
from spj
where jno='j1'and pno='p1'