[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. 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. [4] 14 [4 [4