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Consider the relations City (city_name, state) Hotel (name, address) City_hotel (hotel_name, city_name, owner)
Answer the following queries in relational algebra(i) Find out the names and address of hotels in Agra.(ii) List the names of cities that have no hotel.(iii) List the names of the hotels owned through ‘Taj Group'.
Ans: (i) Π name, address ( σ city_name= ‘Agra' (Hotelname=city_name City_hotel))(ii) Π city_name (City) - Π city_name(City_hotel)(iii) Π hotel_name ( σ owner='Taj Group' (City_hotel))
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
Explain Transaction manager and their work? Transaction Manager: Ensure the database remains in a constant (correct) state despite system failure, and in which concurrent trans
What are stand-alone procedures? Procedures that are not part of a package are called as stand-alone because they independently defined. A good example of a stand-alone procedu
Now that she understands more about the benefits of databases, the play-scheme manager would like to extend the play-scheme database to include data for schools and instructors as
Explain the three data models namely relational, network and hierarchical and evaluate their relative advantages and disadvantages. Hierarchical Model: In hierarchical model, da
Which are the two ways in which entities can participate in a relationship? Total and partial are the two ways in which entities can participate in a relationship
Let us now talk about the relational operations: SELECT The select operation is used to select few specific record from the database based on different criteria, This is a un
Differentiate between a subquery and a join If we need to acquire information from one or more tables after that either subquery or join can be used. If the columns which are t
Define Shared locks? Ans: Shared lock: Throughout concurrent execution of transactions, earlier than a transaction can access a data item, it has to obtain a lock on it. Now he
What is foreign key? Foreign Key - Let there are two relations in tables R and S. Any candidate key of the relation R that is referred in the relation S is known as the forei
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