What is actual difference between delete,drop,truncate ?????

Answer 1

Delete deletes a row of a table.
Truncate deletes all rows of a table.
Drop deletes all rows of a table and the table itself.

By the way, how is that a C# question? Shouldn't you put a sql tag instead?

Answer 2

What about the columns of the tables it won't get deleted ?

Answer 3

If you need to delete columns, then you should change schema with alter table commands, which are different between databases.
And yes, change tag to sql.

Answer 4

Delete : deletes the value
Drop : delete table with structure and data.
Truncate : makes the table empty.

Answer 5

All theses operations r used in different situation. As required.