Oracle Questions

Q:

What do you mean by a tablespace?

Answer

- These are the Logical Storage Units into which a database is divided.
- It is used to group together the related logical structures.

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Subject: Oracle - Technology

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Q:

What is an Index? Explain how to create an Index.

Answer

An index is a object which is used to improve performance during retrieval of records.


CREATE [UNIQUE] INDEX index_name 


ON employee[emp_id, emp_name,dept_id]


[COMPUTE STATISTICS]


The UNIQUE keyword is used when combined values of the index should be unique.


The COMPUTE STATISTICS during the creation of index optimizes the plan of execution of the SQL statement and improves performance.

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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:

Could you explain the areas where tuning of database is required?

Answer

The following are the areas of concern for tuning:


- Memory Usage


- Data Storage


- Data Manipulation


- Physical Storage


- Logic Storage


- Network Traffic


Tuning Memory Usage: In Oracle 10g, we can use the Automatic Workload Repository (AWR) toolset to gather and manage statistical data but in case of Oracle 11g, we can use new initialization parameters such as MEMORY_TARGET to further control the overall memory used by Oracle. It helps us to tune the database automatically when we don’t have time to read the AWR report.


Tuning Data Manipulation: There are two ways to tune Data manipulation in Oracle one way is through Conventional Path mode and second is Direct Path mode.


Tuning Physical Storage: We need to tune the physical storage because it limits the disk in database. This can be done by: Distributing I/O, Striping and Mirroring.

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Subject: Oracle - Technology

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Q:

Explain primary key constraint.

Answer

Primary key constraint ensures that the column(s) always has a unique value to identify the record.
Example:
Below, the primary key is created for column id with name prim_id.
create table employee ( id number NOT NULL, Name varchar(200) Constraint prim_id primary key(id) );

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Subject: Oracle - Technology

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Q:

Define PL/SQL. Explain its purpose

Answer

PL/SQL is Procedural Language SQL that is an extension of SQL that results in a more structural language composed of blocks. It is mainly used in writing applications that needs to be structured and has error handling.

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Subject: Oracle - Technology

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Q:

What is a PeopleSoft database?

Answer

Peoplesoft Database is similar to other database which is used to store data. Peoplesoft database stores data in a table format for system PeopleTools and Application tables. This is independent of the process you use to retrieve that data from PeopleSoft. Inside PeopleSoft database, only three types of tables reside inside the schema: System Catalog tables, PeopleTools tables, and Application data tables. Two of these table types, System Catalog and PeopleTools tables, can be referred to as metadata tables; users make use of Application data tables to store the data they need for their processes.

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Subject: Oracle - Technology

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Q:

What is a sub query? What are its various types?

Answer

- Sub Query also termed as Nested Query or Inner Query is used to get data from multiple tables.
- A sub query is added in the where clause of the main query.

There can be two types of subqueries:
a.) Correlated sub query :
- It can reference column in a table listed in the from list of the outer query but is not as independent as a query.
b.) Non-Correlated sub query :
- Results of this sub query are submitted to the main query or parent query.
- It is independent like a query

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