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Showing Questions 1 - 20 of 111 Questions
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Can we update views.If not,why?

Asked By: meenu | Asked On: May 2nd, 2006

Answered by: naresh kotapati on: Jul 24th, 2014

View is like a logical table we can update view only if single table exist we cannot update view if multiple columns exist

Answered by: gbansal4 on: Dec 14th, 2007

Yes, we can update views.  Point to remember is : Primary key of all the tables should be present in the view.  IT can be a single table or can be 2 or more tables linked in a view.

Primary key

Asked By: kh_trnh | Asked On: Jul 18th, 2008

Why is the choice of primary key important and are three characteristics of an ideal primary key?

Answered by: sanit kale on: Apr 23rd, 2014

The PRIMARY KEY constraint uniquely identifies each record in a database table.

Primary keys must contain unique values.

A primary key column cannot contain NULL values.

Each table should have a primary key, and each table can have only ONE primary key.

Answered by: chaitra murthy on: Jan 16th, 2009

Primary key will let the retrieval operation to be fast.It will not allow you to insert duplicate and null values.It is used to uniquely identify a row in a table.

What is the difference between transaction database and data warehouse databases?

Asked By: Mojtaba Kamalian | Asked On: Apr 8th, 2006

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Answered by: opbang

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Member Since Mar-2006 | Answered On : Sep 24th, 2006

Transaction Database Vs DataWarehouse Database-

1. Transaction Database is Relational Database with the normalised table, whereas DataWarehouse is with denormalised Table.

2. Transaction Database is highly volatile... Designed to maintain transaction of the business Where DataWarehouse is non volatile.. with periodic updates.

3. Transaction Database is OLTP...   Datawarehouse ... is for analysis... 

4. Transaction Database is functional data...  DataWarehouse database Data is subject oriented.

Answered by: kalai on: Jan 29th, 2014

Transactional database means current data in database.
data warehouse means historical data.i.e old data that are flushed out.

Answered by: sreenivas on: Nov 25th, 2012

A transactional database is defined for day-to-day operations like insert, delete and update and in a Datawarehouse databases (OLAP databases) are designed for Analytical purpose. So they require historical data for analysis. These databases are huge databases to store historical data.

Database design questions

Asked By: Muhammad Khan | Asked On: Jan 6th, 2014

I have a database with 5 millions records, I have person table having 5 million records and its have 13 columns. Forename and surname column is heavily populated as compared to other columns. My question is it appropriate to separate forename and surname column and make separate tables for it and reference...

What is the difference between SQL & T-SQL?

Asked By: dhana | Asked On: Jan 23rd, 2007

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Answered by: NITIN TOMER

Answered On : Sep 6th, 2011

sql is a structured query language........and t-sql is implementing on sql server........and t-sql having some more queries than sql .

Answered by: kandriga murali on: Dec 8th, 2013

1) .SQL is non-procedural language since it deals with what data to be extracted.Whereas T-SQL is procedure language since it deals with what data to be executed and how it should be displayed.
2) . SQL can executed only single command whereas T-SQL can executed multiple statement at time.

Answered by: Syed Umar Abbas on: Mar 28th, 2012

Microsoft SQL Server have some more additions to Database Standard Query Language (SQL) is called T-SQL

What is subquerry? Tpes of subqurries? Use of subqurry?

Asked By: chim | Asked On: Jan 27th, 2006

Answered by: Sheraz Baig on: Nov 22nd, 2013

Subquery is basically Query Withing Query.. and the Result of Subquery is used by Outer query and Subquery could be at any level its not level restricted...

Answered by: DIPTENDU HUI on: Jan 28th, 2006

1.Subquery is nothing but a query inside a query which appears only after the WHERE clause of a select statement.2.Two types of subquery is there:a) Co-Related subqueryb) Non-Co-related subquery.3. Us...

SQL* reportwriter is a _____ formatting tool to create simple to sophisticated reports

Asked By: Amarjit | Asked On: Jan 24th, 2007

Answered by: Sheraz Baig on: Nov 22nd, 2013

GUI based

Answered by: manishayadav_1 on: Apr 9th, 2008

menu-driven

What is the difference between delete,drop and truncate?

Asked By: Periyasamy | Asked On: Mar 10th, 2006

Answered by: Sheraz Baig on: Nov 21st, 2013

Delete is DML statement which delete the record/s and can be Rolled Back.
Truncate does same work but because its a DDL statement so cannot be Rolled Back.
Drop is DDL statement which delete the Table structure witht he data, Cannot be Rolled Back.

Answered by: arunkumar on: Jun 18th, 2012

Delete: delete a single row or multiple row it is DML operation so rollback is enable. Truncate: delete from all record in table. commit or rollback is not using. trigger will not fired.but column ...

SQL loader

Asked By: saeedkm | Asked On: Feb 18th, 2009

How does export/import feature differ from that of SQL loader?

Answered by: Sheraz Baig on: Nov 21st, 2013

Totally different Export/Import are oracle utilities to export data in the oracle format and to import the data which is been exported so the format will be the oracle one. While SQL Loader is the u...

Answered by: dhiren21 on: Sep 20th, 2009

Its Different.. For Export we are exporing the data from the Database to a Dump file..i.e EXP from user datafile buffer rows compress etcfor Imprting we are importing the data from a dump file to a da...

Test cases for login screen

Asked By: ranjit rajendran | Asked On: Mar 21st, 2012

Login screen user id -> textbox password -> textbox sign in-> button.. can someone send me how to write test cases for the above requirement?

Answered by: msrajeshreddy on: Oct 25th, 2013

1.enter valid username and valid password.
2.enter invalid username and valid password.
3.enter invalid username and invalid password.
4.enter blank username and valid password.
5.enter valid username and blank password.
6.enter blank username and blank password.

Answered by: pavan naphde on: May 19th, 2012

hi, when someone asked for test cases then test cases must be fulfill all the conditions, 1. Enter Valid User name and valid password And Click On Submit. 2. Enter Valid User name and valid passwor...

SQL query

Asked By: rohitdeepu17 | Asked On: Mar 8th, 2013

How to display nth lowest record in a table for example? How to display 4th lowest (salary) record from customer table?

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Answered by: Yadnesh

Answered On : Jun 1st, 2013

-- First of all Customers table wont have salary attribute. we need to use employees/employeesSalary table -- where we can find salary attribute. -- for finding nth lowest salary record we can obtain derived column using DENSE_RANK() in a subquery and -- obtain temporary result set and finding nth record in a temporary result set using WHERE clause -- for the given example, following is the solution.

Code
  1. SELECT x.rate
  2. ,x.rankedSalary
  3. FROM (SELECT rate
  4.                 ,DENSE_RANK() OVER (ORDER BY rate) AS rankedSalary
  5.                 FROM HumanResources.EmployeePayHistory
  6.                 GROUP BY rate) x
  7. WHERE x.rankedSalary = 4

Answered by: Yadnesh on: Jun 1st, 2013

-- First of all Customers table wont have salary attribute. we need to use employees/employeesSalary table -- where we can find salary attribute. -- for finding nth lowest salary record we can obtai...

Excessive redo generation.

Asked By: muralikasya | Asked On: Mar 5th, 2013

Why excessive redo generation in hot backups ?How to resolve it ?

What is meant by ontology?

Asked By: AnantharajManoj | Asked On: Sep 2nd, 2012

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Answered by: daniel.doboseru

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Member Since Feb-2013 | Answered On : Feb 6th, 2013

An ontology refers to a model that contains a set of classes (individuals) plus a set of relations between them. Lets consider a relational database model, having three tables: Human, Man, Woman. As you can observe, there is no relation defined between them. Well, in an ontology, besides that, you might also have a set of rules like: - Object X is Man, if and only if is Human, but is not Woman. - If object X is Human, then it is either Man or Woman, but not both. For defining ontologies there are several languages developed, the most representative being OWL (Web Ontology Language. And for querying them one must also use a specialized language (eg. SPARQL).

Answered by: daniel.doboseru on: Feb 6th, 2013

An ontology refers to a model that contains a set of classes (individuals) plus a set of relations between them. Lets consider a relational database model, having three tables: Human, Man, Woman. As ...

Multiset table with upi

Asked By: maheshanna | Asked On: Jan 30th, 2013

Multiset table with upi will allow duplicates or not?

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Answered by: daniel.doboseru

View all answers by daniel.doboseru

Member Since Feb-2013 | Answered On : Feb 6th, 2013

UPI stands for Unique Primary Key, which constrain us to have unique keys, thus unique rows. Now even if the Multiset table allows duplicate rows by definition, the UPI constraint overrules it. Answer: No.

Answered by: daniel.doboseru on: Feb 6th, 2013

UPI stands for Unique Primary Key, which constrain us to have unique keys, thus unique rows. Now even if the Multiset table allows duplicate rows by definition, the UPI constraint overrules it.

Answer: No.

Can you store data from a database to excel file without using any tool? How?

Asked By: Cool_Guy007 | Asked On: Sep 3rd, 2012

Answered by: avinash on: Jan 21st, 2013

Yes to store excel file in data base just you have to save the excel file in .CSV(comma delimiter) format and then insert the value as usually in database.....

Answered by: Waqas Ahmed on: Oct 6th, 2012

Here is the query to export data into csv file.

Code
  1. SELECT *
  2. INTO OUTFILE /tmp/products.csv
  3. FIELDS TERMINATED BY ,
  4. ENCLOSED BY "
  5. ESCAPED BY
  6. LINES TERMINATED BY
  7. FROM products

Remove one duplicate column value from multiple

Asked By: chiru099 | Asked On: Sep 13th, 2012

How to remove only one column values from the duplication of values in that column without using any other column references in that table?

Answered by: dhanraj varshney on: Jan 5th, 2013

Two methods..
Use unique key
Run query such way-insert ignore into table.

How many type of implementation methodologies ?

Asked By: Rana Irfan | Asked On: Mar 24th, 2006

Answered by: saratchand on: Dec 8th, 2012

Two type

In software :top down and button up approach
IN DBMS: generalization and specialization other is aggregation

What is the difference between logical and virtual memory in databases

Asked By: Interview Candidate | Asked On: Jan 24th, 2007

Answered by: sarat chand on: Dec 8th, 2012

Logical memory is based on schema design. but virtual memory is based on data access that means we want a data from hard disk(physical memory ) to main memory.

Difference between two tier architecture and three tier architecture?

Asked By: geetha | Asked On: Oct 20th, 2005

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Answered by: Karanjeet

Answered On : Nov 22nd, 2005

Following are the tier types in a client server application:

a. 1 tier application:All the processing is done on one machines and number of clients are attached to this machine (mainframe applications)

b. 2 tier application: Clients and data base on different machines.Clients are thick clients i.e.  processing is done at client side.Application layer is on Clients.

c. 3 tier application.Client are partially thick.Apart from that there are two more layers application layer and database layer.

d. 4 tier application: Some clients may be totally non thick clients some clients may be partially thick and further there are 3 layers web layer, application layer and database layer.

Answered by: Avinash on: Nov 24th, 2012

If I am not wrong

Class variables are variables which we create inside a class.

&

Class member are the variables & function declared inside class.

Answered by: Manoj Kumar Chagantipati on: Jun 12th, 2012

In Two tier there will be Presentation layer and Data base layer
Where as in Three tire there will be Presentation layer,Data access layer and Data base layer

Difference between database & database server?

Asked By: Rana Irfan | Asked On: Mar 24th, 2006

Answered by: iriabije albert on: Nov 6th, 2012

Database is the collection of data in a well manner form

Answered by: RAMAN SHARMA on: Mar 2nd, 2012

Database is called when one computer are not connected with each other and only data are stored in one computer that called database and when computer are connected with each other or particular server so we can access the data every computer its called database server

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