Oracle Questions

Q:

What is personal oracle lite?

Answer

Personal Oracle lite is single user database for distributed and mobile computing. It supports a full range of Java database features as well as advanced replication. Or in other words it is Oracle's lightweight, fully-functional, single-user object- relational database. A small, zero administration embedded database.


Some of the features supported:


- Java Support


- Java Store Procedure Support


- Java triggers Supported


- Multi-column indexing and outer joins.


- Easy to use graphical user interface


- Supports both object and relational database models


- Simultaneous viewing of classes and relational tables

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Subject: Oracle - Technology

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Q:

What is locking ? what are the advantages of locking?

Answer

Locking is a mechanism to ensure data integrity while allowing maximum concurrent access to data. It is used to implement concurrency control when multiple users access table to manipulate its data at the same time.


Advantages :


- Avoids deadlock conditions


- Avoids clashes in capturing the resources

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Q:

What are aggregate functions in SQL? What are those functions?

Answer

Aggregate functions in SQL are used to perform calculation on data. These functions are inbuilt in SQL and return a single value.

SUM( )



SUM function returns the sum or addition of all NOT NULL values of a column. For e.g. I have a Table employee with the fields id, name, salary and I want the sum of all salaries, I can use SUM function as shown
SELECT SUM(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 63,000

AVG( )


 
AVG function returns the average of all NOT NULL values of a column. For e.g. I have a Table employee with the fields id, name, salary and I want the average of all salaries, I can use AVG function as shown
SELECT AVG(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 21,000

COUNT( )



COUNT function returns the number of rows or values of a table. For e.g. I have a Table employee with the fields id, name, salary and I want the count of all rows, I can use COUNT function as shown
SELECT COUNT(*) from employee;

Max ( ) and Min ( )



MAX function returns the largest value of a column in a table. For e.g. I have a Table employee with the fields id, name, salary and I want the maximum salary of an employee, I can use MAX function as shown
SELECT MAX(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 22,000



MIN function returns the smallest value of a column in a table. For e.g. I have a Table employee with the fields id, name, salary and I want the minimun salary of an employee, I can use MIN function as shown
SELECT MIN(emp_salary) from employee;
Hence, if my column emp_salary has values 20,000, 22,000, 21,000; the output will be 20,000

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Subject: Oracle - Technology

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Q:

What is LINQ ?

Answer

LINQ stands for " Language Integrated Query " and it is pronounced as "LINK".
LINQ was introduced in with .NET framework 3.5 including VS2008. It enables you to query the data from various data source like SQL, XML document, ADO .NET data source, web services and any other objects such as Collection, Generics etc...

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Subject: Oracle - Technology

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Q:

What do you mean by Redo Log file mirroring ?

Answer

-  The process of having a copy of redo log files is called mirroring.
-  It is done by creating group of log files together. This ensures that LGWR automatically writes them to all the members of the current on-line redo log group.
-  In case a group fails, the database automatically switches over to the next group. It diminishes the performance.

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Subject: Oracle - Technology

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Q:

Explain how to lock and unlock a user account in Oracle.

Answer

SQL> ALTER USER user_name ACCOUNT LOCK;


SQL> ALTER USER user_name ACCOUNT UNLOCK;

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Subject: Oracle - Technology

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Q:

List the various Oracle database objects.

Answer

- TABLES
- VIEWS
- INDEXES
- SYNONYMS
- SEQUENCES
- TABLESPACES

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Subject: Oracle - Technology

0 2906
Q:

What is ODBC SQLPASSTHROUGH option?

Answer

We use SQLPASSTHROUGH options when we need applications to access data both in the front-end and back-end data servers with a single connection. SQL statements that cannot be executed in the solidDB front-end server are passed over to the back end. 


SQLPASSTHROUGH mode can be set as per session or per transaction. The connection between the front end and back end is made with a back-end compatible ODBC driver which is loaded dynamically in solidDB server.

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