
We as a PHP Drupal web platform developer most often has to face the situation to export data from one table to another table of same database or to table of another database (if site uses multiple databases) during the process of any change in normal work flow.
Most of us normally think to export the data from one table to another by firstly querying the required data from source table and then looping through the query result and inserting them to destination table. This can be simply achieved with a single query.