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21. What is cross join?

Cross join is defined as the Cartesian product of records from the tables present in the join. Cross join will produce result which combines each row from the first table with the each row from the second table. 

22. What are temporal data types in Oracle?

Oracle provides following temporal data types:

• Date Data Type – Different formats of Dates

• TimeStamp Data Type – Different formats of Time Stamp

• Interval Data Type – Interval between dates and time

23. How do we create privileges in Oracle?

A privilege is nothing but right to execute an SQL query or to access another user object. Privilege can be given as system privilege or user privilege. 

[sql]GRANT user1 TO user2 WITH MANAGER OPTION;[/sql]

24. What is VArray?

VArray is an oracle data type used to have columns containing multivalued attributes and it can hold bounded array of values. 

25. How do we get field details of a table?

Describe is used to get the field details of a specified table.

26. What is the difference between rename and alias?

Rename is a permanent name given to a table or a column whereas Alias is a temporary name given to a table or column. Rename is nothing but replacement of name and Alias is an alternate name of the table or column. 

27. What is a View?

View is a logical table which based on one or more tables or views. The tables upon which the view is based are called Base Tables and it doesn’t contain data. 

28. What is a cursor variable?

A cursor variable is associated with different statements which can hold different values at run time. A cursor variable is a kind of reference type. 

29. 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. 

30. What are SET operators?

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

31. How can we delete duplicate rows in a table?

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

32. What are the attributes of Cursor?

Attributes of Cursor are

1. %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.

33. 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. 

34. 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. 

35. What is an ALERT?

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

36. 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. 

37. 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

38. 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.

39. 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.

40. 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

41. What are the differences between LOV and List Item?

LOV is property whereas list items are considered as single item. List of items is set to be a collection of list of items. A list item can have only one column, LOV can have one or more columns. 

42. What are privileges and Grants? 

Privileges are the rights to execute SQL statements – means Right to connect and connect. Grants are given to the object so that objects can be accessed accordingly. Grants can be provided by the owner or creator of an object. 

43. What is the difference between $ORACLE_BASE and $ORACLE_HOME?

Oracle base is the main or root directory of an oracle whereas ORACLE_HOME is located beneath base folder in which all oracle products reside. 

44. What is the fastest query method to fetch data from the table?

Row can be fetched from table by using ROWID. Using ROW ID is the fastest query method to fetch data from the table.

45. What is the maximum number of triggers that can be applied to a single table?

12 is the maximum number of triggers that can be applied to a single table.

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