There are two ways of adding a leading dollar sign to numbers in Oracle. You can either define the column with a number format that displays a number with dollar sign or you can define it in you select statement as follows:
select name, to_char(salary, '$9,999,999,99') from salarytable
to_char() is used to change string formatting. Here we add $ and a comma after every three digits left of the decimal. We also specified that there are two decimal places. Without the 0 in the middle, you would get $.00 instead of $0.00 when the salary is 0.