4 4. (a) Explain the following: The difference between a GROUP BY clause and an ORDER BY clause in SQL. The limitation on the attributes that can be requested in the SELECT clause of an SQL statement if it includes a GROUP BY clause. (b) The following relations form part of a relational database (the relations are self-explanatory): Patient (Patient_ID, Patient_Name) Doctor (Doctor_ID, Doctor_Name) Drug (Drug_ID, Drug_Name) Prescription(Doctor_ID, Patient_ID, Drug_ID, Date) Consultation (Patient_ID, Doctor_ID, Date) With reference to this relational schema, write SQL state- ments for the following queries: i. List the names of doctors who prescribed drug Calpol. [4] 4 ii. List the number of patients who had consultation with Dr Jones. iii. List the names of patients who had been prescribed the same drug more than 5 times. iv. List the names of doctors and the number of consul- tations they had during August 2018, including those who had none during that month