Is it normal to have a second mammogram if you have calcifications?

Yes. Calcs are a very common usually benign mmg finding. Additional views help to characterize the calcifications by their appearance (i.e. Pleomorphic, crushed stone, punctate, etc) which is easier with higher magnfication and compression to smooth out surrounding tissue. Comparing to previous studies helps detect change over time. If they appear benign and there are no priors, a short repeat is ok.
Yes. You are in good company, rachel. As many as 5-10% of all women who get their first screening mammogram are "called back" for a closer look. Very often, the radiologist will classify this as "probably benign" (birads-3), which means they want to repeat a film in 6 months rather than waiting a full year. This is no reason to worry: birads-3 abnormalities are found to be cancerous ~ 1:200 cases.
Yes. A screening mammogram may reveal calcifications seen by the radiologist, or the more subtle ones, by the CAD machine - computerized automated detection unit.To further gualitate and put into a category of relative risk for cancer and decision to biopsy or follow (birads classification) they will bring you back for diagnostic films including magnification views to further assess and localize.
Yes. It is common. The second mammogram is usually comprised of magnification views of the calcifications so the radiologist can get a better view of them. It doesn't mean there is cancer. Most calcifications are benign. Some aren't, which is why it is important to go for the extra views. .