Need to create new output column

I need to create a new output column in a query that will be used as a index.  I    can not use the existing field for security reasons (Col A)  So I must generate a new column (Col B)
Lets say that Col A is a Social Security Number and a call center person can not see it so we will create a new field Col B.  Later internally we will re associate the records.

Col A exists in the table Col B does not.  I can not modify the table

How can I create a query to do this.  A stored procedure will be ok as long as it produces a result set that I can see and export

Example

TableX

Col A           Col B
163777439     1
163777439     1
163777439     1
163777439     1
163777439     1
163777439     1
718108418     2
718108418     2
718108418     2
918233645     3
918233645     3
418323022     4
418323022     4
418323022     4
418323022     4
418434193     5
418434193     5
418434193     5
418434193     5