nalbat=> create table t1 ( .......
CREATE TABLE

nalbat=> copy t1 from stdin;
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
>> .......
>> \.

nalbat=> select count(*) from t1;
 count
-------
      1 
( 1  row)

nalbat=> select count(*) from ( select * from t1 union select * from t1 ) as s1;
 count
-------
      2 
( 1  row)

nalbat=> select count(*) from ( select * from t1 except select * from t1 ) as s1;
 count
-------
      2 
( 1  row)

nalbat=> create table t1 ( );
CREATE TABLE

nalbat=> copy t1 from stdin;
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
>> 
>> \.