Systems, methodologies, media, and other embodiments associated with producing non-repeating random values for use in data masking are described. One example method includes accessing data describing a mask for a value in a database table column to be masked. The example method may also include identifying a number of distinct values in the database table column to be masked and determining a field width for a mask to provide unique random numbers to mask the distinct values. The method may include identifying locations in a mask value to store the unique random value and locations in a mask value to store filler values. The mask value may include different character sets and may comply with user specified formats. The method may include generating a set of statements that when executed produce a mapping table that includes masks for distinct values in the database table column to be masked.