Q&A: Database Basic

Normal DB is under which normal form?
3rd normal form, but sometimes for better performance, can be in 2nd normal form.

What is difference between TRUNCATE, DELETE and DROP commands?
DELETE
The DELETE command is used to remove rows from a table. A WHERE clause can be used to only remove some rows. If no WHERE condition is specified, all rows will be removed. After performing a DELETE operation you need to COMMIT or ROLLBACK the transaction to make the change permanent or to undo it. Note that this operation will cause all DELETE triggers on the table to fire.
TRUNCATE
TRUNCATE removes all rows from a table. The operation cannot be rolled back and no triggers will be fired. As such, TRUCATE is faster and doesn't use as much undo space as a DELETE.
DROP
The DROP command removes a table from the database. All the tables' rows, indexes and privileges will also be removed. No DML triggers will be fired. The operation cannot be rolled back.
DROP and TRUNCATE are DDL commands, whereas DELETE is a DML command. Therefore DELETE operations can be rolled back (undone), while DROP and TRUNCATE operations cannot be rolled back.

What is difference between UNION and UNION ALL?
The Oracle SQL UNION differs from the Oracle UNION ALL primarily because it does not filter out duplicitous rows. The UNION SQL operator returns only the unique rows that appear in either result, while the UNION ALL operator returns all rows in both queries, including duplicate rows.
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:21547067945222

What is Cross Join?
CROSS JOIN returns the Cartesian product of rows from tables in the join. In other words, it will produce rows which combine each row from the first table with each row from the second table. CROSS JOIN serves function as Inner Join if WHERE clause had been added. Vice versa, if INNER JOIN without WHERE clause, it is a cross join.

How to stop a process?
Using KILL command.
http://en.wikipedia.org/wiki/Kill_%28command%29

What is the difference between Inner Join and Outer Join?