What is difference between unique index and simple index?is it possible, two rows can have the same unique index?

sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

Index create on Primary key or unique key is Unique index where as index created on any other element is simple index

srinivasa.dinesh

 Profile Answers by srinivasa.dinesh Questions by srinivasa.dinesh

• Jan 29th, 2008

Unique Index:If the index is for a primary or unique key then the owner, name, type, and columns cannot be modified. These properties are all derived from the key constraint. Changing the name of the ...

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sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

Procedure wont retrun any value but it can return many values on condition. but function always returns a values

shravanam

 Profile Answers by shravanam Questions by shravanam

• Oct 28th, 2007

A procedure is used to perform a specific task. It can also return a value but its not mandatory.But a function is used to perform some calculations and it is mandatory to return atleast one value.

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I tried "truncate table cascadebut I got the error storage keyword is missing (says either drop storage or reuse storage) Can any one help me out.

sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

Write turnicate stmt

vemurisasidhar

 Profile Answers by vemurisasidhar Questions by vemurisasidhar

• Sep 23rd, 2007

If u want to delete a table with constraints i think u need to first disable the constraints on the table and the use truncate table ;alter table disable constraint primary key cascade;

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sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

Dont user select */in/write minimal cond

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sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

SELECT
column_name "Name",
nullable "Null?",
concat(concat(concat(data_type,(),data_length),)) "Type"
FROM user_tab_columns
WHERE table_name=TABLE_NAME_TO_DESCRIBE;

sunildas4U

 Profile Answers by sunildas4U Questions by sunildas4U

• Aug 24th, 2006

An alternative to the DESC command is selecting directly from the data dictionary - DESC MY_TABLEis equivalent to SELECT column_name "Name", nullable "Null?",concat(concat(concat(data_type,'('),data_length),')') "Type"FROM user_tab_columnsWHERE table_name='TABLE_NAME_TO_DESCRIBE';

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sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

1) To protect some of the columns of a table from other users.ie for security purpose.

2)To hide the complexity of a query.

3)To hide the complexity of calculations.

vivekrajece

 Profile Answers by vivekrajece Questions by vivekrajece

• May 19th, 2011

1) To protect some of the columns of a table from other users.ie for security purpose.2)To hide the complexity of a query.3)To hide the complexity of calculations.

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What is the use of NULLIF function in SQL?

sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

In SQL, NullIf function is used to compare two expressions. There are 3 possible results for NULLIF. 1. If the values are same, NullIf returns NULL. Eg: NULLIF(Prem,Prem) returns NULL 2. If they are...

Prem_p

 Profile Answers by Prem_p Questions by Prem_p

• Apr 28th, 2011

In SQL, NullIf function is used to compare two expressions. There are 3 possible results for NULLIF.1. If the values are same, NullIf returns NULL. Eg: NULLIF('Prem','Prem') returns NU...

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What is the Aggregation Key?

sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

This is the composite key

AnithaLetchumi

 Profile Answers by AnithaLetchumi Questions by AnithaLetchumi

• Aug 10th, 2011

Aggregation Key is nothing but composite or concatenated key. It's the primary key having more than one column. For example different books may have identical titles, authors. In this case we can take...

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What is use of lock query in SQL Plus? Give its syntax and implementation?

sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

Exclusive Lock: This is placed when Insert, Update or Delete command is performed. There can be only one exclusive lock on a record at a time.

hussasha

 Profile Answers by hussasha Questions by hussasha

• Mar 17th, 2009

Locking protect table when several users are accessing the same table. Locking is a concurrency control technique in Oracle. It helps in data integrity while allowing maximum concurrency access to...

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EXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returns a value.

rohitosu

 Profile Answers by rohitosu Questions by rohitosu

• Mar 9th, 2012

As a rule of thumb IN should be used when the sub query will return small result set. It should be kept in mind that the sub query should not return null values. EXISTS should be used when the result set returns large result set. Other factors that might affect query performance is the indexes

Vineet Arya

 Profile Answers by Vineet Arya Questions by Vineet Arya

• Sep 17th, 2011

Which is more faster - IN or EXISTS? It totally depends upon the query. For some queries Exist is efficient and for some IN is efficient Exits is correlated sub query, in which the outer query run f...

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I have to tables A and B. My records in this table are in such a way that

Table A Table B

10 15
11 16
12 10
13 11

Question :- I want only the 10 and 11 records as my output.

Can anyone help me out ( 5 ways...

hussain

• Mar 29th, 2012

Code
 

SivaKumar

• Mar 23rd, 2012

Method 1

Code
 

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What is difference between nested query,sub query and nested query? explain clearly with an example?

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arpitapatel  

 Profile Answers by arpitapatel Questions by arpitapatel

• Member Since Sep-2008 | Sep 24th, 2008

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Query inside the query is nested query.
It is also called as sub query.
Correlated subquery runs once for each row selected by the outer query. It contains a reference to a value from the row selected by the outer query.

Nested subquery runs only once for the entire nesting (outer) query. It does not contain any reference to the outer query row.

rams

• Apr 3rd, 2012

Both are same

katgeektalk

 Profile Answers by katgeektalk Questions by katgeektalk

• Aug 22nd, 2010

The subquerry is often reffered to as a nested SELECT, sub-SELECT, or inner SELECT statement. The subquery generally excuted first, and its output is used to complete the query condition for the main (or outer) query.

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What is a SET operator? What are the types what is the difference between SET operators and JOINS?

Aparna

• Apr 5th, 2012

Union --> All rows/cols from 1st select and 2nd select with no duplicates Union All -->All rows/cols from 1st Select and 2nd Select with duplicates Intersect --> Rows common in both select statements...

dajjaal

 Profile Answers by dajjaal Questions by dajjaal

• Sep 20th, 2010

The UNION operator is used to combine the result-set of two or more SELECT statements.   SQL joins are used to query data from two or more tables, based on a relationship between certain columns in these tables.

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farhan

• Apr 20th, 2012

Code
 

uma

• Mar 6th, 2012

Select * from emp a
where salary >(select avg(salary) from emp b where a.dept_no = b.dept_no);

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ngoudjou albert

• May 22nd, 2012

We use the selfjoin on the table employees to retrieve the job before thier managers

Code
 

janardhan g

• Aug 7th, 2011

Select x.ename from emp x,emp y where x.mgr=y.empno and x.hiredate

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mfasiur

 Profile Answers by mfasiur Questions by mfasiur

• Jun 7th, 2012

Also, the undo blocks will store all the data until the transaction is either committed or rolled back.So, if someone issues DML statements(insert,update & delete)The before image of the transaction i...

Hany

• Jun 7th, 2012

With No Commit after delete , you will be able to see all record in session 2

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How to retrieve data from two tables of different servers

Sujaya

• Jun 8th, 2012

SELECT Ename, DeptNo, Sal, Emp.DeptNo, Dept.Dname, Dept.Loc, Dept FROM
Emp, Dept
WHERE Emp.DeptNo = Dept.DeptNo;

sampra

 Profile Answers by sampra Questions by sampra

• Mar 6th, 2012

You can use join

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maverickwild  

 Profile Answers by maverickwild Questions by maverickwild

• Member Since Nov-2005 | Nov 15th, 2005

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Try this

select sal from (select * from order by sal asc) where rownum < 3

snehal Falke

• Jul 13th, 2012

Select * FROM emp ORDER BY sal ASC LIMIT 2

mohit

• Jun 28th, 2012

If you want to employee name then query is given below

Code
 

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Arbind Kumar Singh

• Jul 23rd, 2012

sql query for retrieving last row particular column value depending upon its ID??? QUERY: select top 1 [column_name1],[column_name2] from [table_name] where ID=[ID_value] order by index desc here i...

Ambarish

• Apr 19th, 2012

Select last(column_name) from Table.

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No.

Shantanu

• Aug 17th, 2012

You cant directly use commit in triggers. You have to use PRAGMA Autonomous_Transaction or you can call other procedure or function, but other procedure or function should also have PRAGMA Autonomous_Transaction in it.

Jagan

• Aug 21st, 2011

Yes, by using autonomous transaction

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