November 1, 2018

Sreekanth B

Hitachi Most Frequently Asked Latest Oracle Interview Questions Answers

What Is Data Block?

Oracle database’s data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk.

What Is Network Database Link?

Network database link is created and managed by a network domain service. A network database link can be used when any user of any database in the network specifies a global object name in a SQL statement or object definition.

Whether any commands are used for Months calculation? If so, What are they?

In Oracle, months_between function is used to find number of months between the given dates. Example is –

Months_between(Date 1, Date 2)

What Are Benefits Of This Version?

Oracle Virtual Directory aggregates identity sources without consolidation.
Additionally OVD 11g is the only virtual directory on the market that comes with enterprise-class monitoring and reporting in a default configuration.

What Are The Key New Features Of Ovd?

Unified Directory services administration via Oracle Directory Services Manager (ODSM).
Deployment accelerators.
Centralized Fusion Middleware log and auditing.
Unified Identity Management installer.
Automated synchronization of OVD cluster configurations.

What Platforms Are Supported?

Supported platforms are listed on the Oracle Fusion Middleware 11g platform certification Matrix.

Can Oracle Directory Services Manager Be Used To Manage Older Versions?

No – ODSM can only be used to manage 11g.
Hitachi Most Frequently Asked Latest Oracle Interview Questions Answers
Hitachi Most Frequently Asked Latest Oracle Interview Questions Answers

What are nested tables?

 Nested table is a data type in Oracle which is used to support columns containing multi valued attributes. It also hold entire sub table.

What is COALESCE function?

COALESCE function is used to return the value which is set to be not null in the list. If all values in the list are null, then the coalesce function will return NULL.

Coalesce(value1, value2,value3,…)

What is BLOB datatype?

A BLOB data type is a varying length binary string which is used to store two gigabytes memory. Length should be specified in Bytes for BLOB.

How do we represent comments in Oracle?

Comments in Oracle can be represented in two ways –

Two dashes(–) before beginning of the line – Single statement
/*—— */ is used to represent it as comments for block of statement

 Difference between varchar and varchar2 data types?

Varchar can store upto 2000 bytes and varchar2 can store upto 4000 bytes. Varchar will occupy space for NULL values and Varchar2 will not occupy any space. Both are differed with respect to space.

In which language Oracle has been developed?

Oracle has been developed using C Language.

What is RAW datatype?

RAW datatype is used to store values in binary data format. The maximum size for a raw in a table in 32767 bytes.

What is the use of NVL function?

The NVL function is used to replace NULL values with another or given value. Example is –

NVL(Value, replace value)

What is DML?

Data Manipulation Language (DML) is used to access and manipulate data in the existing objects.  DML statements are insert, select, update and delete and it won’t implicitly commit the current transaction.

What is key preserved table?

A table is set to be key preserved table if every key of the table can also be the key of the result of the join. It guarantees to return only one copy of each row from the base table.


The WITH CHECK option clause specifies check level to be done in DML statements. It is used to prevent changes to a view that would produce results that are not included in the sub query.

What is the use of Aggregate functions in Oracle?

Aggregate function is a function where values of multiple rows or records are joined together to get a single value output. Common aggregate functions are –


How can we view last record added to a table?

Last record can be added to a table and this can be done by –

Select * from (select * from employees order by rownum desc) where rownum<2;
Select * from (select * from employees order by rownum desc) where rownum<2;

What is the data type of DUAL table?

The DUAL table is a one-column table present in oracle database.  The table has a single VARCHAR2(1) column called DUMMY which has a value of ‘X’.

What is difference between Cartesian Join and Cross Join?

There are no differences between the join. Cartesian and Cross joins are same. Cross join gives cartesian product of two tables – Rows from first table is multiplied with another table which is called cartesian product.

Cross join without where clause gives Cartesian product.

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