How to fetch SQL incremental data

Hi I need help to fetch SQL incremental data using log stash6.1.2..

There is no id field in SQL table and we have to achieve this combining 2 columns hostname & sampletime which will be unique all the time

You don't need an id column, but you do need a column or set of columns that you can add to a condition to select only those rows that have changed since last time. Wouldn't the sample time column do?