a2zinterviews

21.	What are the transaction properties?
	Atomicity Consistency Isolation Durability

22.	Define Synonym?
	Synonym is an alternative method to creating a view that includes the entire table or view from another user it to create a synonym. A synonym is a name assigned to a table or view that may thereafter be used to refer to it.

23.	What is an active database?
	Active database is a database that includes active rules, mostly in the form of ECA rules(Event Condition rules). Active database systems enhance traditional database functionality with powerful rule processing cabalities, providing a uniform and efficient mechanism for database system applications.

24.	What is the difference between a HAVING CLAUSE and a WHERE CLAUSE?
	HAVING can be used only with the SELECT statement. HAVING is typically used in a GROUP BY clause. When GROUP BY is not used, HAVING behaves like a WHERE clause. Having Clause is basically used only with the GROUP BY function in a query whereas WHERE Clause is applied to each row before they are part of the GROUP BY function in a query.

25.	What are the purpose of Normalisation?
	Minimize redundancy in data. Remove insert, delete and update anamoly during the database activities. Reduce the need to reorganize data it is modified or enhanced. Normalisation reduces a complex user view to a set of small and stable subgroups of fields or relations.