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DataBase Administrator (DBA) Interview Questions and Answers

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(Continued from previous part...)

114. What are the uses of rollback segment?

If we find any problem after data manipulation and if we want to undo it, then we can use this ROLLBACK segment.
SAVEPOINT is the command used to save the workdone. After saving data, if we want to perform insertion/deletion and we done it wrongly, then we can ROLLBACK it by using the SAVEPOINT.

Ex:
SAVEPOINT s1;
ROLLBACK s1;


115. What is a deadlock and Explain?

Waiting for an event that never happens or processed.
Ex : Say there are three process P1, P2, P3 and three resources R1, R2, R3.
(1) P1 is started and it is using R1.
(2) P2 is started and it is using R2.
(3) P3 is started and it is using R3.


To complete process P1 it needs resource R2 which is currently used by P2.
To complete process P2 it needs resource R3 which is currently used by P3.
To complete process P3 it needs resource R1 which is currently used by P1.

In this case each and every process is waiting for unoccured events. This situation we called as DEADLOCK.
To prevent this concept is there called DEADLOCK PREVENTION.


116. State any three mouse events system variables?

System.mouse_button_pressedSystem.mouse_button_shift


117. What other parts of your organization do you interact with and how?

Again, if you have exhausted question 1 and 2 you may never get to this question. But if you have been apprehensive to opening up and explaining yourself, take note that you may have an issue and the interviewer might also be already getting tired of the interview process. If you get to this question consider yourself in trouble. You really need to forget all your hang-ups and start explaining what it is that you like to do as a DBA, and why you want to work for this particular company. You are going to have to reel this interviewer back into the interview process or you might not get to the true technical question part of the interview.


118. How do you display console on a window?

The console includes the status line and message line, and is displayed at the bottom of the window to which it is assigned. To specify that the console should be displayed, set the console window form property to the name of any window in the form. To include the console, set console window to Null.


119. In exception handling we have some NOT_FOUND and OTHERS. In inner layer we have some NOT_FOUND and OTHERS. While executing which one whether outer layer or inner layer will check first?

Once you got inside the OUTER_LOOP, it comes out only after the NOTFOUND statement.

So OUTER_LOOP will be valuated first.Its similar to ‘C’ language, first OUTER_LOOP will valuated followed by an INNER_LOOP.


120. What are the different types of joins?

Different Types of Joins-
Inner Join
Outer Join - Right Outer Join
Left Outer Join
Cross Join


121. How will you copy the structure of a table without copying the data?

Answer1
create table xyz
as ( select * from abc where 1=0)

Answer2
create table New_tbl as select * from Old_tbl where rownum

Answer3
select top 0 * into xyz from try


122. What is a VIEW? How to get script for a view?

Answer1
View is a logical perspective of a Table. It is a predefined set of query on a table through which we can perform any kind of select queries instead of redefining the condition every time. Update or Insert Statements cannot be performed through this.

Answer2
Update or Insert statements cannot be performed ON View. Answer3
Update or Insert statements cannot be performed ON View is not correct.
As I know, if a view meets certain criteria you can update it and such operation will be reflected in the original table. Also, if you are using materialized view, you can insert or update it.

(Continued on next part...)

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