select query not returning expected result I have a table which is having 30 columns. And I have executed the below query (using postgres 9.1, executed via pgAdmin)

select column2 || '|' || column3 || '|' || column4 
from tablename 
order by column1 asc


I am getting 5 rows with empty result. and I noticed that column3 having values as 'Data1|Data2' while I execute select * from table name.

Any idea?

Table structure is simple. All are character varying except column1 (numeric) and data having simple texts except column3. Column3 having data with delimer ("|). i.e., 12345|23333

How can I achieve the same in this? 

psql -d mydb-U user1 -c "\copy tablename to 
    '/home/user/table_data.csv' delimiter '|' csv header";
If any of the columns is null the result of the concatenation using || is also null. 

You can use concat() or even concat_ws() ("concat With Separator") to make Postgres treat null values like empty strings:

select concat_ws('||', column2, column3, column4)
from tablename 
order by column1 asc;


Note that concat_ws() will not append the separator if a value is "missing". If you do need it, you have to use concat()

select concat(column2, '||', column3, '||', column4)
from tablename 
order by column1 asc;


Details in the manual: 

9.4. String Functions and Operators

Regarding the last part of your question, you can use a select statement for the \copy command. For details please see the manual.