Skip to main content

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.

Labels:

Comments

Post a Comment

Popular posts from this blog

Question 8: Aggregate Functions

Examine the description of the STUDENTS table: STD_ID NUMBER(4) COURSE_ID VARCHARD2(10) START_DATE DATE END_DATE DATE Which two aggregate functions are valid on the START_DATE column? (Choose two) A. SUM(start_date) B. AVG(start_date) C. COUNT(start_date) D. AVG(start_date, end_date) E. MIN(start_date) F. MAXIMUM(start_date) Answer: C & E Explanation: It is possible to apply COUNT() and MIN() functions on the column with DATE data type. Incorrect Answers A: Function SUM() cannot be used with DATE data type column. B: Function AVG() cannot be used with DATE data type column. D: Function AVG() cannot be used with DATE data type column, and function AVG() just has one parameter X, not two. It averages all X column values returned by the SELECT statement. F: There is no MAXIMUM() function in Oracle, only MAX() function exists.
Post a Comment
Read more

19. Oracle Processes

Processes Oracle uses many small (focused) processes to manage and control the Oracle instance. This allows for optimum execution on multi-processor systems using multi-core and multi-threaded technology. Some of these processes include: PMON - Process Monitor SMON - System Monitor ARCn - Redo Log Archiver LGWR - Redo Log Writer DBWn - Database Writer CKPT - Checkpoint process RECO - Recoverer CJQn - Job Queue Coordinator QMNn - Queue-monitor processes Dnnn - Dispatcher Processes (multiplex server-processes on behalf of users) Snnn - Shared server processes (serve client-requests) MMAN - Internal process (used for internal database tasks) LSP0 - Logical standby coordinator process (controls Data Guard log-application) MRP - Media-recovery process (detached recovery-server process) MMON - Memory-monitor process MMNL - Memory monitor light (gathers and stores AWR statistics) PSP0 - Process-spawner (spawns Oracle processes) RFS - Remote file server process (archive to a remote site) DBRM ...
Post a Comment
Read more

20. TRIM Function

Which SELECT statement will the result 'elloworld' from the string 'HelloWorld'? A. SELECT SUBSTR( 'HelloWorld',1) FROM dual; B. SELECT INITCAP(TRIM ('HelloWorld', 1,1)) FROM dual; C. SELECT LOWER(SUBSTR('HellowWorld', 1, 1) FROM dual; D. SELECT LOWER(SUBSTR('HelloWorld', 2, 1) FROM dual; E. SELECT LOWER(TRIM ('H' FROM 'HelloWorld')) FROM dual; Answer: E Explanation: TRIM function accept a string describing the data you would like to trim from a column value. It can trim from both side of column value i.e. left and right. In the following statement this functionwill trim as SELECT LOWER(TRIM ('+' FROM 'HelloWorld')) FROM dual; From the above statement trim function will remove the character 'H' from 'HelloWorld' and LOWER function will convert the remaining character to lower case.
Post a Comment
Read more