Skip to main content

Question 7: Group By

Examine the description of the EMPLOYEES table:

EMP_ID NUMBER(4) NOT NULL
LAST_NAME VARCHAR2(30) NOT NULL
FIRST_NAME VARCHAR2(30)
DEPT_ID NUMBER(2)
JOB_CAT VARCHARD2(30)
SALARY NUMBER(8,2)

Which statement shows the maximum salary paid in each job category of each department?


A.SELECT dept_id, job_cat, MAX(salary) FROM employees
WHERE salary > MAX(salary);

B.SELECT dept_id, job_cat, MAX(salary) FROM employees
GROUP BY dept_id, job_cat;

C. SELECT dept_id, job_cat, MAX(salary) FROM employees;

D. SELECT dept_id, job_cat, MAX(salary) FROM employees
GROUP BY dept_id;


Answer: B


Explanation:
This answer provides correct syntax and semantics to show the maximum salary paid in each job category of each department.



Incorrect Answers

A: This query will not return any row because condition SALARY > MAX(SALARY) is FALSE.

C: This query will return error because you cannot show maximum salary with DEPT_ID and JOB_CAT without grouping by these columns.

D: The GROUP BY clause is missing JOB_ID column.

E: You don't need to group results of query by SALARY in the GROUP BY column.
Labels:

Comments

Post a Comment

Popular posts from this blog

Question 5: Where and having clauses

Which two statements are true about WHERE and HAVING clauses? (Choose two) A. A WHERE clause can be used to restrict both rows and groups. B. A WHERE clause can be used to restrict rows only. C. A HAVING clause can be used to restrict both rows and groups. D. A HAVING clause can be used to restrict groups only. Answer: B, C Explanation : HAVING clause to specify which groups are to be displayed and thus further restrict the groups on the basis of aggregate information. The Oracle server performs the following steps when youuse the Having clause 1. rows are grouped 2. the group function is applied to the group 3. the group that match the criteria in the Having clause are displayed. WHERE clause cannot be use to restrict groups HAVING clause use to restrict groups WHERE clause cannot be use when there is group functions. Incorrect Answers : A. Where clause cannot be use to restrict groups D. When HAVING clause is use rows are grouped as well.
Post a Comment
Read more

21.Oracle - The self documenting dictionary

Oracle - The self documenting dictionary Oracle's Data dictionary is itself self documenting. we can query DICTIONARY AND DICT_COLUMNS views for descriptions of the data dictionary views and their columns. The following query gives the descriptions of all of the data dictionary views. SELECT table_name, comments FROM dictionary ORDER BY table_name; It gives the large amount of output. By using where class we can focus a smaller set of views as like the following query. SELECT table_name, comments FROM dictionary WHERE table_name LIKE '%TABLE%' ORDER BY table_name It returns all views containing the word 'TABLE' Like wise We can query the DICT_COLUMNS view also. It gives the descriptions for the columns for all views. Following query retrieves descriptions for the columns in ALL_TAB_COLUMNS. SELECT column_name, comments FROM dict_columns WHERE table_name = 'ALL_TAB_COLUMNS'; This is a sample one. We can learn lot about oracle through data d...
1 comment
Read more

Question 15

Write a PL/SQL Program for the following output --*-- -***- ***** -***- --*-- Answer The output based on the value of 'n' declare n number(2) default 20; i number(2); j number(2); h number(2); s number(2); b varchar2(1) default 'I'; begin s := 1; if n mod 2 = 0 then n := n+1; end if; h := n/2 -1; for i in 1..n loop for j in 1..h loop dbms_output.put('-'); end loop; for j in 1..s loop dbms_output.put('*'); end loop; for j in 1..h loop dbms_output.put('-'); end loop; dbms_output.put_line(' '); if n = s then b := 'D'; end if; IF b='I' then s := s+2; h := h-1; else s := s-2; h := h+1; end if; end loop; end;
Post a Comment
Read more