CREATE TABLE Medication (Code VARCHAR, name VARCHAR)
CREATE TABLE patient (SSN VARCHAR)
CREATE TABLE Prescribes (patient VARCHAR, Medication VARCHAR)

Find the number of patients who are not using the medication of Procrastin-X.
SELECT COUNT(*) FROM patient WHERE NOT SSN IN (SELECT T1.patient FROM Prescribes AS T1 JOIN Medication AS T2 ON T1.Medication = T2.Code WHERE T2.name = 'Procrastin-X')
WITH "_u_0" AS (SELECT "T1"."patient" FROM "Prescribes" AS "T1" JOIN "Medication" AS "T2" ON "T1"."Medication" = "T2"."Code" AND "T2"."name" = 'Procrastin-X' GROUP BY "patient") SELECT COUNT(*) FROM "patient" LEFT JOIN "_u_0" AS "_u_0" ON "SSN" = "_u_0"."" WHERE "_u_0"."" IS NULL