I am getting this error ORA-00907: missing right parenthesis

Question

create table passenger(pnr number(10) primary key,
trainnumber number(5) foreign key references train(trainnumber),
noofseats number(4),
price number(4),
doj varchar2(10))

ORA-00907: missing right parenthesis

Answer 1

The foreign key expression is redundant (read: wrong). The syntax is just to add references :

create table passenger(pnr number(10) primary key,
trainnumber number(5) references train(trainnumber), -- here
noofseats number(4),
price number(4),
doj varchar2(10))

Answer 2

change yout CREATE TABLE statement to be like below

create table passenger(pnr number(10) primary key,
trainnumber number(5), 
noofseats number(4),
price number(4),
doj varchar2(10),
foreign key (trainnumber) references train(trainnumber))