How to use sqlplus SPOOL command:

Using spool command we can generate output files in client machine:

SQL>conn manjit/manjit;
connected

 SQL> Spool on
SQL> set heading off <===
SQL> Spool /oradata/backup/spooltext.txt
SQL> Query(sql query)
SQL> Spool off

We create a file in D:\External_Tables named emp_query.sql with the following saved query. 

SELECT EMPNO ||',' || ENAME || ',' || SAL || ',' || COMM FROM EMP; 

SQL> CONN manjit/manjit@pro 
Connected. 

 SQL> SET FEEDBACK OFF HEADING OFF ECHO OFF 
 SQL> SPOOL D:\External_Tables\emp.csv 
 SQL> @D:\External_Tables\emp_query.sql 
 SQL> SPOOL OFF 

To view the content of the file from SQLPLUS, type.. 

SQL> host type D:\External_Tables\emp.csv