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9.	What is the difference between DELETE and TRUNCATE statements?
	DELETE is a Data Manipulation Language (DML) statement and can be rolled back while TRUNCATE is a DDL statement and cannot be rolled back. You can delete data selectively by using the DELETE statement while TRUNCATE statement removes all data in the table. DELETE does not affect High Water Mark (HWM) while TRUNCATE moves HWM to the beginning of the table.
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10.	Can you build indexes online?
	Yes, you can build indexes online.
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11.	What are the different types of indexes available in Oracle?
	Oracle database provides several indexing schemes that provide complementary performance functionality, which are given as follows: B–tree index – Retrieves a small amount of data from a very large table. B–tree cluster index – Refers to the index that is defined specifically for cluster. Hash cluster index – Refers to the index that is defined specifically for a hash cluster. Global and local index - Relates to partitioned tables and indexes. Reverse key index – Refers to the index that is most useful for Oracle Real Application Clusters applications. Bitmap index – Uses a map of bits to represent the whole index. They are mostly used in data warehouses. These indexes work best for columns with a small set of values. Function based index – Contains the pre computed value of a function or expression. Domain index – Refers to an application or cartridge.
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12.	What is null?
	Oracle has a specific value called null, which is neither equal nor not equal to any value. In addition, null is neither true nor false. A value can be checked for null using special operator called IS NULL or IS NOT NULL.
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