> 1. I have three daughters who became nurses.
> 2. I have three daughters, who became nurses.

I got the answers from [here](http://ell.stackexchange.com/questions/88763/what-is-the-difference-between-two-sentence-in-meaning) before but some says that the comma makes some differences, others says that there is no difference. Please, tell me the difference in meaning when the comma is added.