retriving  concurrent and validate data

...when there is a possibility of duplication of tuple's 

i.e. retrieve only one tuple for every n tuples's matching the
     criteria


 

the timestamp offers the most efficient means organizing data in 
relational table ...it serve's the purpose of a primary key  and 
what may also be termed as row-id in some products currently available


given the context of a primary key , unique key , candidate key's

...when there is a possibility of duplication of tuple's

a)   retriving  concurrent and validate based on timestamp offers most
flexible means of organizing the data

b) a trigger or other mean's that sets a flag on the tuple with latest 
   timestamp ...and either remove's or changes the flag code previous
   tuple that matched the criteria minus the time stamp.




   