Sync and Erase?

I have many songs on my iPhone that were purchased on this same device. I would like to sync music from my computer onto my iPhone and I would like to know if this action could delete the purchased content from my phone. Does anyone know something about that?

As you can find in the official Apple Support website, you can redownload or transfer your iTunes Store purchases from an iPhone, iPad, or iPod to a computer, without of course losing your purchase in the mobile device.

I quote:

If you purchased items from the iTunes Store and you've stored them on only your iOS device or iPod, you can transfer them to any computer that is authorized with your Apple ID.

The easiest way to add past iTunes Store purchases to your iOS device is to redownload them from iTunes in the Cloud. You can also transfer your purchases from your device to your computer.