shital Rathod

• Nov 24th, 2021

This solution best in oracle ,but decode () is not work in mysql.
can you take in mysql and giv me the proper query regarding this question.

Mercy

• Oct 29th, 2018

Hope the below query will answer the question."sql SELECT COUNT(*) total, SUM(decode(to_char(hire_date,yyyy),1995,1,0)) "1995", SUM(decode(to_char(hire_date,yyyy),1996,1,0)) "199...

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Kolta Sam  

 Profile Answers by Kolta Sam Questions by Kolta Sam

• Member Since Jul-2011 | Jul 10th, 2011

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Primary Key:

It is a visible key
It generated by user or application.
It could be changed by the user or application.
It could be queried
It used to form a relation between tables
It shouldn’t contain null value
It resemble table row
It is a unique identifier for a table object.
It contains only one key
It could contain numeric and strings characters.
It is an unique key which each row contain a distinct different key.
Example for it is a customer_Id.
It always starts by number one and second is two and so on but can starts with a different number.
Could created on one or more columns
No duplicate records

Secondary Key:

It used to form a relation between tables.
It is alternate table key.
It used to search data with primary key
It could contains null value
It could contains more than one secondary key for each table
Created only on one columns
No duplicate records
It creates index clustered by default

Surrogate Key:

It is invisible key for the user or the application.
It resembles database entity.
It generated by the system so it is invisible for user and application.
It shouldn’t contain null values
Only one surrogate key for each data entity
Its value is unique system wide.
Its value is never manipulated by the user or the application.
It never reused
It is frequently sequential number
It called synthetic key, an entity identifier, a system-generated key, a database sequence number, a factless key, a technical key, or an arbitrary unique identifier
No duplicate records

gopi

• May 18th, 2018

Primary key not allow null values where as unique allows but both are alternates.
surrogate key serve as primery key in type 2 dimension tables

Sukdya

• Nov 27th, 2017

Primary key doest not allow null values but unique key allows only one null value.

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Dnyaneshwar Mane

• Apr 25th, 2018

DUAL is a special one-row and 1-column table having value "X" by default in Oracles SYS schema. This table can be used for the purpose of : 1. Calculating mathematical expressions like: SELEC...

shadiq

• Jun 25th, 2015

Insert into dual values (Y); will work i guess, only thing is you need a sufficient privilege...
Also Dual can have 1000 columns and only one row.

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To put the definition of an entity is an entity is a single person, place, or thing about which data can be stored. That is in other words for example when one wants to store information about STUDENT then it has details like studentno, student name, address for communication, phone number, class of the student and so on. All of these details together is placed in the entity or table called as STUDENT....

Ravi

• Oct 31st, 2017

Set of attribute is called entity

Adarsha

• Aug 18th, 2017

Difference between entity and attributes
entity is the table name
and
attribute is the column name of the table

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ArafatZG

• Sep 28th, 2017

POST will temporary save data in the relevant table.
If you do not use COMMIT after POST then the temporary saved data will be lost.
COMMIT permanently Save Data in the table

Mohammed Abdul Afroze

• Oct 30th, 2007

The Difference between post and commit are as follows:Post:In oracle we never find such command post.Commit:The changes will be made permenently from the redo log buffers to the redo log files.

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Anusha

• Apr 27th, 2017

The removal of duplications is known as normalization . The advantage is it improves the performance of DBMS.

Subrat

• Jul 28th, 2015

It is a Process to obtain a database design that allows for efficient access and storage of data. This process use reduce data redundancy and the chances of data becoming inconsistent.

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What is the purpose of Mviews? Outline the difference between refresh types? How to refresh the MView?

gyana

• Apr 24th, 2017

Dbms_mview.refresh(materialize view name)

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What is the difference between IS and AS in Oracle PL/SQL..?

kishanjha

 Profile Answers by kishanjha Questions by kishanjha

• Feb 28th, 2017

IS is for defining and AS is for ALIAS only

Nupur

• Apr 24th, 2015

In plsql there is no difference.

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kishanjha

 Profile Answers by kishanjha Questions by kishanjha

• Feb 26th, 2017

Trigger are different from Constraints.
Both supports data integrity but trigger can be imposed on more than one tables.
Triggers can be used to take table backups and changes logs. Like what was the old value, who updated (user) and when (update time)

munny

• Jul 24th, 2015

Triggers are the stored procedures that are fired when an DB event occur where as Constraints are the checks or the rules that are enforced on data columns to maintain the data integrity. Both can be...

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Answered by: Saumendra Mohanty

• May 16th, 2006

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Both Replace and Translate are single row functions in Oracle 9i.

The Replace Function replaces single character with multiple characters.

But in Translate Function replaces sinlge character with sinlge character only.

Manickavel

• Dec 26th, 2016

Translate is used for character by character substitution where as Replace is used for substituting a character with a word

shaikh siraj

• Apr 24th, 2016

String to string changing is called as replace.
Character to character changing is called as translate.

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Shaheed

• Dec 14th, 2016

ORDER BY statement is worng, as we cant put alias in order by clause

shivam srivastava

• Sep 29th, 2016

Code
 

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Ajit bartakke

• Aug 24th, 2016

Pro*C is a Pre-compiler tool and OCI is a intermidator

Adas

• Nov 1st, 2012

Can anyone tell the exact diff b/w Pro*C and OCI

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What is the amount of performance improvement you get with doing BULK COLLECT? I tried answering I will measure with the cost.. but the interviewer wants a specific answer. Is there any general formula for deriving the cost improvement based on the no. of records processed in bulk fetch?

Nikhil Inamdar

 Profile Answers by Nikhil Inamdar Questions by Nikhil Inamdar

• Jul 4th, 2016

Generally for millions of records, BULK COLLECT performs very much faster. If we compare BULK COLLECT and normal CURSOR FOR LOOP then BULK COLLECT can perform almost 4 times faster.
You can create your own program and use DBMS_UTILITY.GET_TIME for comparing the results.

dinesh

• Feb 3rd, 2013

We can limit the bulk binding values. It would improve the overall performance. It would not consume more memory.

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Suzanne

• Apr 26th, 2016

The information is stored in the alter log. It will tell you which datafile is corrupt and you will be able to recover using RMAN

SATHEES KUMAR

• Jul 1st, 2015

Control file is a small binary file that record the physical structure of the database like datafile and redolog file location, timestamp,scn and used for recover purpose all so but have no datafile backup then you cant recover the database.

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Which is the subset of SQL commands used to manipulate Oracle database structures, including tables?

test

• Jan 5th, 2016

DDL is used to define database structure (cerate , alter, drop, truncate)
DML is used to manipulate data ( select, insert, update, delete)
So DDL is used to manipulate database

sri ram reddy

• Nov 14th, 2015

Alter command manipulates Oracle database structures including tables

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Explain the difference between object view and relational view.

Diptiman

• Dec 21st, 2015

A "Relational View" is the projection of the data using simple relational tables like: CREATE OR REPLACE VIEW relational_view (employee_name, department_name) AS SELECT employee_name, department_na...

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SRI RAM REDDY

• Nov 14th, 2015

Truncate is DDL command, not a DML command When we issue Truncate on a database table, the records are deleted from the table, and structure remains same. Once we issue truncate on a table, the record...

Akshatha

 Profile Answers by Akshatha Questions by Akshatha

• Dec 25th, 2014

Truncate is DDL. Auto commits the transaction. Also, truncating a table can reset the high water mark if REUSE storage clause is not used.

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Which one will give best performance between GROUP BY function in Oracle and GROUP BY function in Crystal Reports? Explain

Shyam

• Oct 22nd, 2015

The Group BY in Oracle will give best performance, because Group By is not a function for Oracle.

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rishipahuja  

 Profile Answers by rishipahuja Questions by rishipahuja

• Member Since Aug-2006 | Aug 6th, 2006

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rowid has a physical significance i.e you can read a row if you know rowid. It is complete physical address of a row.

While rownum is temporary serial number allocated to each returned row during query execution.

vinay

• Sep 20th, 2015

It it will be re-assigned to a different row when inserted by Oracle.

Arif

• Jul 3rd, 2015

I have one doubt like you said that rowid is automatically created when we add a row(record) then what happens to rowid
when we delete that record?

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Balaji

• Aug 5th, 2015

The way for accessing a remote object.

maqk

• Jan 2nd, 2006

What's the Difference between COM and DCOM?Obviously, the difference is that DCOM is distributed but COM is not. To be more precise, there are three main elements added to COM: The way for creating a ...

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