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Explain Instance and schemas?
Instances and schemas: Databases changes over time as the information is deleted and inserted. The collection of information stored in database at a particular moment in time is known as Instances and the whole design of database is known as schemas.
Information about a bank is about customers and their account. Customer has a name, address that consists of house number, area and city, and one or more phone numbers. Account ha
What does the cardinality ratio specify? Mapping cardinalities or cardinality ratios state the number of entities to which another entity can be associated. Mapping cardinaliti
To do the division operation R1 ÷ R2, R2 should be a correct subset of R1. In the following example R1 have attributes A and B and R2 have only attribute B so R2 is a correct subse
Mixed fragmentation: Sometimes, horizontal fragmentation or vertical fragmentation of a database schema by itself is insufficient to sufficiently distribute the data for some appli
Question: (a) Why is it important to know the architecture rather than to start requirement capture when designing a large scale system? (b) Who are the different people in
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.
In a relation, tuples are not inserted in any definite order. Ordering of tuples is not defined as a part of a relation definition. Though, records may be structured later accordin
What is the role of ORDER By Clause? ORDER BY clause: The ORDER BY clause permits you to sort the records in your result set. The ORDER BY clause can just be used in select s
Saving Derived Attributes to Avoid Re-computation Data that is derived from other data should be stored in the computed form to avoid re-computation. For this, we could define
How does the two phase protocol ensure serializability in database schedules? Ans: A transaction is termed to follow the two-phase locking protocol if all locking operations
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