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Oracle Sample Questions : Oracle Interview Questions

91. What's the length of SQL integer ?

    Answer: 32 bit length

92. What is the difference between foreign key and reference key ?

    Answer: Foreign key is the key i.e.attribute which refers to another table primary key. Reference key is the primary key of table referred by another table.

93. Can dual table be deleted, dropped or altered or updated or inserted ?

    Answer: Yes

94. If content of dual is updated to some value computation takes place or not ?

    Answer: Yes

95. If any other table same as dual is created would it act similar to dual?

    Answer: Yes

96. For which relational operators in where clause, index is not used ?

    Answer: <> , like '%...' is NOT functions, field +constant, field||''

97. .Assume that there are multiple databases running on one machine.How can you switch from one to another ?

    Answer: Changing the ORACLE_SID

98. What are the advantages of Oracle ?

    Answer: Portability : Oracle is ported to more platforms than any of its competitors, running on more than 100 hardware platforms and 20 networking protocols. Market Presence : Oracle is by far the largest RDBMS vendor and spends more on R & D than most of its competitors earn in total revenue.This market clout means that you are unlikely to be left in the lurch by Oracle and there are always lots of third party interfaces available. Backup and Recovery : Oracle provides industrial strength support for on-line backup and recovery and good software fault tolerence to disk failure.You can also do point-in-time recovery. Performance : Speed of a 'tuned' Oracle Database and application is quite good, even with large databases.Oracle can manage > 100GB databases. Multiple database support : Oracle has a superior ability to manage multiple databases within the same transaction using a two-phase commit protocol.

99. What is a forward declaration ? What is its use ?

    Answer: PL/SQL requires that you declare an identifier before using it.Therefore, you must declare a subprogram before calling it.This declaration at the start of a subprogram is called forward declaration.A forward declaration consists of a subprogram specification terminated by a semicolon.

100. What are actual and formal parameters ?

     Answer: Actual Parameters : Subprograms pass information using parameters.The variables or expressions referenced in the parameter list of a subprogram call are actual parameters.For example, the following procedure call lists two actual parameters named emp_num and amount:
     Eg.raise_salary(emp_num, amount);

     Formal Parameters : The variables declared in a subprogram specification and referenced in the subprogram body are formal parameters.For example, the following procedure declares two formal parameters named emp_id and increase:
     Eg.PROCEDURE raise_salary (emp_id INTEGER, increase REAL) IS current_salary REAL;