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126.	What are check constraint?
	A Check constraint is used to limit the values that can be placed in a column. The check constraints are used to enforce domain integrity.
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127.	What is database Trigger?
	A database trigger is a PL/SQL block that can defined to automatically execute for insert, update, and delete statements against a table. The trigger can e defined to execute once for the entire statement or once for every row that is inserted, updated, or deleted.
	Discuss Sivakoti, said Jan 18,2014 A trigger is a pl/sql block structure which is fired when a dml statements like insert, delete, update is executed on a d/b table. Your Name Your Email-ID Your Answer

128.	What is DataWarehousing?
	According to Bill Inmon, known as father of Data warehousing. “A Data warehouse is a subject oriented, integrated ,time variant, non volatile collection of data in support of management’s decision making process”.
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129.	Define Sequence?
	A Sequence is a database object that can be used to provide very quick generation of unique numbers.
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130.	Define View?
	A View is a database object that is a logical representation of a table. It is derived from a table but has no longer of its own and often may be used in the same manner as a table. A view is a virtual table that has columns similar to a table. A view does not represent any physical data.
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