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What are views? Explain how views are different from tables?
A view in SQL terminology is a one table in which is derived from other tables. These other tables could be base tables or previously described views. A view does not necessarily exist in physical form; it is considered a virtual table, in contrast to base tables, whose tuples are infact stored in the database. This limits the possible update operations in which can be applied to views, but it does not provide any limitations on querying a view. A view represents a variant perspective of a base relation(s). The definition of a view in a form view statement is stored in the system catalog. Any attribute in the view could be updated as long as the attribute is simple and not derived from a computation including two or more base relation attribute. View that includes a join may or may not be updatable. Such views are not updatable if they do not include the primary keys of the base relations.
We define a view in SQL through using the create view command. To describe a view, we must provide the view a name and must state the query in which computers the view. The form of
What is NULL? Simply NULL means not in value.
Data Independence This brings us to our next topic: data independence. It is the property of the database which tries to make sure that if we make any change in any level of sc
What is meant by Physical blocks? The input and output operations are completed in block units. The blocks residing on the disk are referred to as physical blocks.
Can a domain, assigned to a data element be changed? Yes. We can do so by just overwriting the entry in the field domain.
In case of entity integrity, the primary key may be declared? In a case of entity integrity primary key may be not Null.
What are the disadvantages of file processing system? The drawbacks of file processing systems are a) Data redundancy and inconsistency b) Complexity in accessing data
What is the purpose of storage manager? The storage manager is responsible for the following a) Interaction with the file manager b) Translation of DML commands in to low
Single-Valued Dependencies A database is a collection of related information and it is therefore inevitable that some items of information in the database would depend on some
A use case diagram giving a pictorial overview of user requirements and brief use case descriptions. As the case study contains only an outline of a business scenario, you will als
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