OCA /OCP Oracle Database 11g A ll-in-One Exam Guide- P53:There is an ever increasing demand for staff with IT industry certification. The benefits to employers are significant—they can be certain that staff have a certain level of competence—and the benefits to the individuals, in terms of demand for their services, are equally great. Many employers are now requiring technical staff to have certifications, and many IT purchasers will not buy from firms that do not have certified staff. | OCA OCP Oracle Database 11g All-in-One Exam Guide 476 Include or Exclude Grouped Rows Using the HAVING Clause Clustering rows using a common grouping attribute with the GROUP BY clause and applying an aggregate function to each of these groups returns group-level results. The HAVING clause provides the language to limit the group-level results returned. The HAVING clause may only be specified if there is a GROUP BY clause present. All grouping is performed and group functions are executed prior to evaluating the HAVING clause. Self Test 1. What result is returned by the following statement SELECT COUNT FROM DUAL Choose the best answer. A. NULL B. 0 C. 1 D. None of the above 2. Choose one correct statement regarding group functions. A. Group functions may only be used when a GROUP BY clause is present. B. Group functions can operate on multiple rows at a time. C. Group functions only operate on a single row at a time. D. Group functions can execute multiple times within a single group. 3. What value is returned after executing the following statement SELECT SUM SALARY FROM EMPLOYEES Assume there are ten employee records and each contains a SALARY value of 100 except for one which has a null value in the SALARY field. Choose the best answer. A. 900 B. 1000 C. NULL D. None of the above 4. Which values are returned after executing the following statement SELECT COUNT COUNT SALARY FROM EMPLOYEES Chapter II Group Functions 477 Assume there are ten employee records and each contains a SALARY value of 100 except for one which has a null value in their SALARY field. Choose all that apply. A. 10 and 10 B. 10 and NULL C. 1 0 and 9 D. None of the above 5. What value is returned after executing the following statement SELECT AVG NVL SALARY 100 FROM EMPLOYEES Assume there are ten employee records and each contains a SALARY value of 100 except for one employee who has a null value in the SALARY field. Choose the best answer. A. NULL B. 90 C. 100 D. None of the above 6. What value
