Here's the entire update query:
UPDATE Health_History SET Health_History.HeartAttackDOD = Null, Health_History.AnginaDOD = Null, Health_History.IrregularHeartDOD = Null, Health_History.OtherHeartDOD = Null, Health_History.StrokeDOD = Null, Health_History.FainitingDOD = Null...