how to select max of mixed string/int column?

Question

Lets say that I have a table which contains a column for invoice number, the data type is VARCHAR with mixed string/int values like:

invoice_number
*********         


        

Answer 1

After a while of searching I found the easiest solution to this.

select MAX(CAST(REPLACE(REPLACE(invoice_number , 'HKL', ''), '', '') as int)) from invoice_header