Oracle Database Interview Questions & Answers Set-2

1. What is null value? 
Ans: Null Value is neither zero nor it is a blank space. It is some unknown value which occupies 4 bytes of space of memory in SQL.

2. Define transaction? 
Ans: A transaction is a sequence of SQL statements that Oracle Database treats as a single unit.

3. What is the difference between sql & oracle? 
Ans: SQL is Stuctured Query Language.Oracle is a Database. SQL is used to write queries against Oracle DB.

4. What are different Oracle database objects?
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5. What is hash cluster? 
Ans: A row is stored in a hash cluster based on the result of applying a hash function to the rows cluster key value. All rows with the same hash key value are stores together on disk.

6. What is a User_exit?
Ans: Calls the user exit named in the user_exit_string. Invokes a 3GI program by name which has been properly linked into your current oracle forms executable.

7. What is schema?
Ans: A schema is collection of database objects of a user.

8. What are Roles?
Ans: Roles are named groups of related privileges that are granted to users or other roles

9. What are the dictionary tables used to monitor a database spaces? 

10. What is a SNAPSHOT?
Ans: Snapshots are read-only copies of a master table located on a remote node which is periodically refreshed to reflect changes made to the master table.

11. What is an ALERT?
Ans: An alert is a window which appears in the center of the screen overlaying a portion of the current display.

12. What is an integrity constraint?
Ans: 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.

13. What are SET operators?
Ans: SET operators are used with two or more queries and those operators are Union, Union All, Intersect and Minus.

14. What are cursor attributes?
Ans: 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.

15. What is a cursor variable?
Ans: 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.