List out patient names with calcium deficiency.
patient names = first, last; calcium deficiency refers to observations.DESCRIPTION = 'Calcium' and observations.VALUE < 8.6;
SELECT DISTINCT T1.first, T1.last FROM patients AS T1 INNER JOIN observations AS T2 ON T1.patient = T2.PATIENT WHERE T2.DESCRIPTION = 'Calcium' AND T2.VALUE < 8.6