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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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shaik shamsheer

• Dec 28th, 2011

In case of varchar it store upto 2000 bytes and in case of varchar2 it stores 4000 bytes
varchar is occupies space for the null value and varchar2 does not occupy space for null values.

venkat

• Dec 4th, 2011

"varchar" allocates memory in dynamic fashion where as "varchar2" also allocates memory in dynamic fashion but it also supports garbage collection.
"varchar" is developed along with SQL where as "varchar2" is developed by Oracle.

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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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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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Vijay Shewale

• Sep 11th, 2014

The reason behind char is still in oracle that is some of the table and objects are stored in oracle in char data types. to support that data types for that it is still in oracle. one more thing that ...

Paras

• Feb 23rd, 2013

To Provide backward compatibility. i.e. program written in older version of Oracle might have CHAR used in it. The newer version should be compatible with it. Thats why CHAR is still there in Oracle ..

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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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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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Difference between oracle8i and oracle9i.

Zeeshan

• Aug 3rd, 2007

SGA: System Global Area. Its a chuck of memory used on oracle processes.

kodaliprakash

 Profile Answers by kodaliprakash Questions by kodaliprakash

• Jul 14th, 2007

Oracle 8i also allows column dropping.

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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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lipika mishra

 Profile Answers by lipika mishra Questions by lipika mishra

• Aug 22nd, 2012

1.CHAR should be used for storing fix length character strings. String values will be space/blank padded before stored on disk. If this type is used to store varibale length strings, it will waste a l...

lina

• Aug 22nd, 2012

1.CHAR should be used for storing fix length character strings. String values will be space/blank padded before stored on disk. If this type is used to store varibale length strings, it will waste a l...

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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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Create a matrix query to display the job, the salary for that job based on department number and the total salary for that job, for departments 20,50,80, and 90,giving each column and appropriate heading.

sachin

• Apr 18th, 2012

Select job,
sum(decode(deptno,10,sal)) deptno10,
sum(decode(deptno,20,sal)) deptno20,
sum(decode(deptno,30,sal)) deptno30,
sum(decode(deptno,40,sal)) deptno40
from emp group by job order by 1;

Neha

• Sep 25th, 2011

Select job in job, sal in salary, sum(salary) in total_sal
where job=(select job in job where deptno=20 and 50 and 80 and 90)
;

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Iyappan

• Feb 24th, 2012

Select job, count(job) from emp group by job;

z_ashwini

 Profile Answers by z_ashwini Questions by z_ashwini

• Jan 13th, 2012

Code
 

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SQL>DECLARE 2 dayofweek VARCHAR2(200); 3 BEGIN 4 SELECT TO_CHAR(sysdate,'Day') INTO dayofweek FROM DUAL ; 5 6 IF dayofweek = 'Tuesday' 7 THEN 8 DBMS_OUTPUT.PUT_LINE('Aloha!!! Today Is Tuesday'); 9 ELSE 10 DBMS_OUTPUT.PUT_LINE('Today is '||to_char(sysdate,'Day')); 11 END IF; 12 END; 13 /Today is TuesdayPL/SQL procedure successfully completed.SQL>What's...

kperumal75

 Profile Answers by kperumal75 Questions by kperumal75

• May 2nd, 2011

It should be (sysdate,'day')

shri_b

 Profile Answers by shri_b Questions by shri_b

• Mar 12th, 2010

Use trim(dayofweek) in IF Condition

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ashishpandey52

 Profile Answers by ashishpandey52 Questions by ashishpandey52

• Nov 12th, 2008

select e_name,e_salary from emp where e_salary=(select min(e_salary)  from (select e_salary from emp order by sal desc )where rownum<4; 

myhotinterview

 Profile Answers by myhotinterview Questions by myhotinterview

• Jun 3rd, 2008

I think we can also use this:select emp_name from from where rownum=3 order by salary desc

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ACE_GEEK  

 Profile Answers by ACE_GEEK Questions by ACE_GEEK

• Member Since Jul-2008 | Jul 22nd, 2008

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"C" ofcourse!!!

sirih1

 Profile Answers by sirih1 Questions by sirih1

• May 24th, 2011

Oracle is developed using C and C++

matabrez

 Profile Answers by matabrez Questions by matabrez

• Nov 6th, 2010

Till 9i it was developed in using "C" and Java langauge. But from 10g it is fully developed in Java.

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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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rc

• Aug 15th, 2014

CONSTRAINTS:= 1.it will check the existing data and feature data. 2.we cant change the constraint behavior these are predefined. 3.constraint are not support the object tables. 4.constraints can crea...

vishnuvardhanarao

• Nov 14th, 2012

Check constraints it cant work multiple tables

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devarapalli rohini

 Profile Answers by devarapalli rohini Questions by devarapalli rohini

• Oct 14th, 2011

Select * from employees where hiredate in (1995,1996,1997,1998);

Prashanth

• Oct 10th, 2011

Exact query you required..... Try it out if you have any doubts.

Code
span style="color: #ff0000;">'yyyy''yyyy''yyyy');

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venkat

• Dec 4th, 2011

From Oracle 9i it allows maximum 1000 columns in a table. In Oracle 8i, it only allows 256 columns in a table.

ambinu

 Profile Answers by ambinu Questions by ambinu

• Jun 14th, 2011

MySQL: Maximum number of columns in one table - 3398; size of a table row - 65534 (BLOB and TEXT not included). Oracle: Unlimited rows@table. Maximum number of columns in one table - 1000. Up to 32 columns in index key. PostgreSQL: Rows - unlimited, columns - 1600; size of a table row - 1.6TB.

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