arju@TERMINUS>create table dept (dept_id number );

Table created.

arju@TERMINUS>create table std (id number);

Table created.
arju@TERMINUS>alter table std add primary key (id);

Table altered.

arju@TERMINUS>alter table dept add foreign key(dept_id) references std(id);

Table altered.

arju@TERMINUS>host exp arju/arju tables=dept file=/backup/check.dmp

Export: Release 10.2.0.2.0 - Production on Sat Oct 20 23:50:02 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options
Export done in US7ASCII character set and AL16UTF16 NCHAR character set
server uses WE8ISO8859P1 character set (possible charset conversion)

About to export specified tables via Conventional Path ...
. . exporting table                           DEPT          0 rows exported
Export terminated successfully without warnings.
arju@TERMINUS>drop table dept;

Table dropped.

arju@TERMINUS>drop table std;

Table dropped.

arju@TERMINUS>create table std( id number);

Table created.

arju@TERMINUS>host imp arju/arju file=/backup/check.dmp full=y

Import: Release 10.2.0.2.0 - Production on Sat Oct 20 23:53:12 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options

Export file created by EXPORT:V10.02.01 via conventional path
import done in US7ASCII character set and AL16UTF16 NCHAR character set
import server uses WE8ISO8859P1 character set (possible charset conversion)
. importing ARJU's objects into ARJU
. importing ARJU's objects into ARJU
. . importing table                         "DEPT"          0 rows imported
IMP-00017: following statement failed with ORACLE error 2270:
 "ALTER TABLE "DEPT" ADD FOREIGN KEY ("DEPT_ID") REFERENCES "STD" ("ID") ENAB"
 "LE"
IMP-00003: ORACLE error 2270 encountered
ORA-02270: no matching unique or primary key for this column-list
Import terminated successfully with warnings.

ORA-00921: unexpected end of SQL command