SELECT empno || lpad(ename, 10,'.' )"fuse # Name" from emp where rownum < 7

CONCAT () is the same as ||

PostgreSQL :

SELECT empno || lpad(ename, 10,'.' )"fuse # Name" from emp limit 7

CONCAT () is the same as ||

MySQL : (less accommodating)

SELECT concat(empno,"...", sal)"emp#-sal" from emp limit 7

CONCAT () is not  same as ||