Hi Brian
thanks for your comment, you are right but there's not enough. We want to know this numbers evolution month by month. Just like this
January February March April June ...
Survey sent: 392 427 581 822 901
Survey answered 85 98 110 145 223
Satisfaction index 4,7 4,4 4,4 4,8 4,7
Then, the "satisfaction index" is calculated by answers, and, because we have the received date at table survey_answer, is possible to calculate the evolution mont by month.
The same occurs with the "survey answered", because with the same "received date" we can obtain this numbers.
But there's no way to obtain the first line, because there aren't anywhere data about survey's sent if there aren't answered.
Any idea?
Thank you