Do both parents have to have the sickle cell trait for the child to have sickle cell anemia?

No. 2 abnormal (sickle cell) gene have to be inherited to have sickle cell disease. This can happen if both patents have sickle cell trait, one parent has sickle cell disease or both have sickle cell disease.
Yes or Sickle cell. The sickle cell anemia is passed to a child from both parents who must have at least a single sickle gene to pass. Either parent must have trait or another hemaglobin varient that includes a sickle gene. (ss, sc, sa trait).