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Question-   a) Consider a database with objects A, B, and C, and the following two transactions T₁ and T₂ involving those objects: T₁ T₂ begin_transaction begin_transaction read(A) read(A) read(B) read(B) read(C) read(C) If A = 13, B …

Solution-

a) The Initial values of A, B, and C is given as:

A = 13

B = 13

C = 10

The database consistency requirement is: either A = 13 or B = 13

The Two transactions are given as:

 

b) Database Consistency: it allows only valid data to be written to the database. if any transaction violates the database consistency rules, then entire transaction will be rolled back to its previous state (i.e. original previous state) otherwise the transaction moves from one consistent state to other consistent state.

it is important to regulates the data that is coming into transactions and rejects the datas that doesn't fit into their rules.

 

c) The Relational Algebra is given as:

\prodemployeeNumber, lastName, firstName, DeptName((\sigmaPosition = 'Manager'Employees) \Join Departments)

 

The SQL Query corresponds to given Relational Algebra is:

SELECT employeeNumber, lastName, firstName, DeptName

FROM Employees, Departments

WHERE Position = 'Manager'

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