1. Which date function is used to find the difference between two dates ?

MONTHS_BETWEEN

2. The IN operator may be used if you know the exact value you want to return for at least one of the columns.

SELECT column_name FROM table_name WHERE column_name IN (value1,value2,..)

3. What are the pre-requisites to modify datatype of a column and to add a column with NOT NULL constraint ?

- To modify the datatype of a column the column must be empty.
- To add a column with NOT NULL constrain, the table must be empty.

4. If a view on a single base table is manipulated will the changes be reflected on the base table ?

If changes are made to the tables and these tables are the base tables of a view, then the changes will be reference on the view.

5. Why is the most of the processing done at the sever ?

To reduce the network traffic and for application sharing and implementing business rules.

6. Union - Union is the product of two or more tables.

7. Intersect - Intersect is the product of two tables listing only the matching rows.

8. What are the privileges that can be granted on a table by a user to others?

Insert, update, delete, select, references, index, execute, alter, all.

9. What is referential integrity constraint?

Maintaining data integrity through a set of rules that restrict the values of one or more columns of the tables based on the values of primary key or unique key of the referenced table.

10. NVL

NVL : Null value function converts a null value to a non-null value for the purpose of evaluating an expression. Numeric Functions accept numeric I/P & return numeric values. They are MOD, SQRT, ROUND, TRUNC & POWER.