Skip to main content

References to DBMS Concepts


Many of you may have some concern on Basics of DBMS and about the definitions of R-DBMS, H-DBMS and N-DBMS. Some of you might have studied the concepts little different than the one I have defined on my site, but nevertheless definitions and concepts(DBMS) on my site are simple and easy to understand which are explained at a very basic level. Am collating some links which will provide similar and more detailed definitions and insight on DBMS concepts.

DBMS and its history -- http://en.wikipedia.org/wiki/Database_management_system
Types of DBMS -- http://en.wikipedia.org/wiki/Types_of_DBMS
                              http://sqlserver-guide.blogspot.com/2009/05/data-base-system-models-or-types-of.html
Notes from Penn State University, USA -- http://www.personal.psu.edu/glh10/ist110/topic/topic07/topic07_06.html
Flat File Database -- http://en.wikipedia.org/wiki/Flat_file_database
Hierarchical DBMS -- http://en.wikipedia.org/wiki/Hierarchical_database_model
Network DBMS -- http://en.wikipedia.org/wiki/Network_model_(database)
Relational DBMS -- http://en.wikipedia.org/wiki/Relational_model
Database(Do not get confused with so much information, treat this link as a reference) -- http://en.wikipedia.org/wiki/Database


Hope this clears the confusion in air.



Comments

rashmi dhiman said…
hello sir....i want a suggestion from u,can i do manual testing and QTP together...will it effect my study or any other loss???
Mithun Ashok said…
Hi Rashmi Dhiman,

If you want you can take do both Manual and QTP together only thing is you have to put in lot of effort and concentrate on both the topics.

It is suggested to take these courses one after the other so you get enough time to study.

Regards,
Mithun
TEJ said…
I'm looking for enotes of complete SQL notes.

Plz guide me as to which is the best book to refer!

With regards,
Tej G.K
Mithun Ashok said…
Hi Tej,

Follow the link below,

http://www.mithunashok.com/2011/04/basics-of-rdbms.html

Mithun
TEJ said…
Hi Mithun,

Thank you :)

With regards,
Tej G.K
TEJ said…
Hi Mithun,

I have small confusion between ROUND and TRUNC operator's.

Can you tel me the answers for the following qn's are right or wrong .
ROUND( 1742.471,-1) -> 1740
ROUND( 1742.471,-2) -> 1700
ROUND( 1742.471,-3) -> 2000

TRUNC( 1742.471,-1) -> 1740
TRUNC( 1742.471,-2) -> 1700
TRUNC( 1742.471,-3) -> 1000


Let me know if any answers wrong and explanat it plz.
HARISH MENARIA said…
Sir, Plz tell us that what would be the series of initial 5 questions that u would be asking in an inrterview ??
HARISH MENARIA said…
SIR,
Plz tell us that what would be the initial 5 questions that u yould b asking in an interview on SQL .
Mithun Ashok said…
Hi Tej,

Execute these number functions and let me know if you have any queries.

Regards,
Mithun
Mithun Ashok said…
Hi Harish,

Will write an article on this gimme some time.

Regards,
Mithun
naresh n said…
hello sir........ i installed oracle software...in that i entered password(system) and thre not asking any username by during installation....after completing sucessful installation its asking username also what can i do now...........?
Mithun Ashok said…
Hi Naresh,

Use scott as username and tiger as password.

Regards,
Mithun
Usha.V said…
Hi sir:) we have to display name,hire date,day of the week on which the emp started n order bt the day of the week starting with monday.
i wrote the query as:
SELECT ename,hiredate,to_char(hiredate,'DAY')as day
FROM emp
ORDER BY day=to_char(hiredate,'MONDAY');
but im nt getting the desired result. wht changes shld i do sir
Smruti said…
Hi Sir Please give the bellow questions answers.

What is the difference between trigger and constraint? Give more than five difference
Mithun Ashok said…
Hi Usha,

Refer to the article below,

Sorting by day of the week

Regards,
Mithun
Mithun Ashok said…
Hi Smruti,

Triggers are used to execute some procedure in case of database events.

Constraint are the restrictions that you can have on each column.

Regards,
Mithun
vamshi said…
hii sir, i have to learn some basics of pl/Sql and oracle apps for that what all is the basic knowledge required and can u mail me some useful material for this since i din't find in this site
DIRECTION SKY said…
wish you a very very happy deepawali sir.....
uday said…
wish you a very very happy deepawali sir....
Amit Jha said…
i found this on internet...hope it will be useful for you..."http://www.red-gate.com/products/sql-development/sql-prompt/entrypage/effortlessly?utm_source=cp&utm_medium=email&utm_term=5593&utm_content=effortlessly&utm_campaign=sqlprompt"
Dipan saha said…
Sir i am confuse about DBMS and RDBMS.Please tell me the different
deepak r said…
Mithun sir u are awesome, awesome teaching, interactive blog... great
saket singh said…
sir somehow meanwhile installation sql plus i missed unlocking scott....now in the username & password field what should i enter to access the s/w.......plz recommend me some suggestions

Popular posts from this blog

SQL Interview Questions on Subqueries

SUB Queries:
1. List the employees working in research department 2. List employees who are located in New York and Chicago
3. Display the department name in which ANALYSTS are working
4. Display employees who are reporting to JONES
5. Display all the employees who are reporting to Jones Manager
6. Display all the managers in SALES and ACCOUNTING department
7. Display all the employee names in Research and Sales Department who are having at least 1 person reporting to them
8. Display all employees who do not have any reportees
9. List employees who are having at least 2 reporting
10. List the department names which are having more than 5 employees
11. List department name having at-least 3 salesman
12. List employees from research and accounting having at-least 2 reporting
13. Display second max salary
14. Display 4th max salary
15. Display 5th max salary  -- Answer for nth Max Salary
Co-Related Subqueries:
16. Write a query to get 4th max salary from EMP table
17. Write a query to get 2nd…

Answers for SUB Queries

1. SQL> select empno, ename from emp where deptno=(select deptno from dept where dname='RESEARCH');


2. SQL> select empno, ename from emp where deptno in (select deptno from dept where loc in ('NEW YORK','CHICAGO'));

3. SQL> select dname from dept where deptno in ( select deptno from emp where job ='ANALYST');

4. SQL> select empno, ename, mgr from emp where mgr = (select empno from emp where ename='JONES');

5. SQL> select empno, ename, mgr from emp where mgr = (select mgr from emp where ename='JONES')

6. SQL> select empno, ename, job from emp where deptno in ( select deptno from dept where dname in ('SALES','ACCOUNTING'))

7. SQL> select empno, ename, job from emp where deptno in ( select deptno from dept where dname in ('SALES','RESEARCH')) and empno in (select mgr from emp)

8. SQL> select empno, ename from emp where empno not in ( select mgr from emp where mgr is not null)

9. select…

'Linux-x86_64 Error: 28: No space left on device' While trying to start the database -- Error

SQL> startup mount pfile='/tmp/initdlfasp12.ora'
ORA-27102: out of memory
Linux-x86_64 Error: 28: No space left on device


This as you can see is on Linux x86 with 64 bit processor. We got this error after we changed SGA on 10gR2 database. So was sure that this is something to do with the OS.

Parameters to check for this are shmall.

shmall is the total amount of shared memory, in pages, that the system can use at one time.

$cat /proc/sys/kernel/shmmax
53687091200

$ getconf PAGE_SIZE
4096

As per Oracle SHMALL should be set to the total amount of physical RAM divided by page size.

Our system has 64GB memory, so change kernel.shmall = 1024 * 1024 * 1024 * 64 / 4096 = 16777216


Once this value is calculated you can modify Linux system configuration file directly.

$ su - root
vi /etc/sysctl.conf file:
kernel.shmall=16777216

and

# sysctl -p

Once this is done the database was started without any problem.