October 10, 2018

Sreekanth B

TCS Most Frequently Asked Latest Oracle Interview Questions Answers

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 –

Average
Count
Sum

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;
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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.
TCS Most Frequently Asked Latest Oracle Interview Questions Answers
TCS Most Frequently Asked Latest Oracle Interview Questions Answers

Can we store pictures in the database and if so, how it can be done?

Yes, we can store pictures in the database by Long Raw Data type. This datatype is used to store binary data for 2 gigabytes of length. But the table can have only on Long Raw data type.

What is an integrity constraint?

An integrity constraint is a declaration defined a business rule for a table column. Integrity constraints are used to ensure accuracy and consistency of data in a database. There are types – Domain Integrity, Referential Integrity and Domain Integrity.

What is an ALERT?

An alert is a window which appears in the center of the screen overlaying a portion of the current display.

What is hash cluster?

Hash Cluster is a technique used to store the table for faster retrieval. Apply hash value on the table to retrieve the rows from the table.

What are the various constraints used in Oracle?

Following are constraints used:

NULL – It is to indicate that particular column can contain NULL values
NOT NULL – It is to indicate that particular column cannot contain NULL values
CHECK – Validate that values in the given column to meet the specific criteria
DEFAULT – It is to indicate the value is assigned to default value

What are cursor attributes?

Each cursor in Oracle has set of attributes which enables an application program to test the state of the cursor. The attributes can be used to check whether cursor is opened or closed, found or not found and also find row count.

What are SET operators?

SET operators are used with two or more queries and those operators are Union, Union All, Intersect and Minus.

How can we delete duplicate rows in a table?

Duplicate rows in the table can be deleted by using ROWID.

What are the attributes of Cursor?

Attributes of Cursor are

%FOUND
Returns NULL if cursor is open and fetch has not been executed

Returns TRUE if the fetch of cursor is executed successfully.

Returns False if no rows are returned.

%NOT FOUND
Returns NULL if cursor is open and fetch has not been executed

Returns False if fetch has been executed

Returns True if no row was returned

%ISOPEN
Returns true if the cursor is open

Returns false if the cursor is closed

%ROWCOUNT
Returns the number of rows fetched. It has to be iterated through entire cursor to give exact real count.

What is difference between SUBSTR and INSTR?

SUBSTR returns specific portion of a string and INSTR provides character position in which a pattern is found in a string.

SUBSTR returns string whereas INSTR returns numeric.

What is the parameter mode that can be passed to a procedure?

IN, OUT and INOUT are the modes of parameters that can be passed to a procedure.

What are the different Oracle Database objects?

There are different data objects in Oracle –

Tables – set of elements organized in vertical and horizontal
Views  – Virtual table derived from one or more tables
Indexes – Performance tuning method for processing the records
Synonyms – Alias name for tables
Sequences – Multiple users generate unique numbers
Tablespaces – Logical storage unit in Oracle.

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