What are the drawbacks of using File system over database ma

What are the drawbacks of using File system over database management system? List three responsibilities of a database-management system. For each responsibility, explain the problems that would arise if the responsibility were not discharged. Explain the distinctions among the terms primary key, candidate key. and super key. Consider the bank database. |0.5+0.5+1=2 Marks] branch! branch name, branch city, assets) customer (customer name, customer street, customer city) loan (loan number, branch name, amount) borrower (customer name, loan number) account (account number, branch name, balance) (customer name, account number) Give an expression in the relational algebra for each of the following queries: Find all loan numbers with a loan value greater than S50.000. Find the names of all depositors who have an account with a value greater than $9,000. Find the names of l depositors who have an account with a value greater than S8.000 at the \"Uptown\" branch.

Solution

1) Disadvatages of File System: a) Data Mapping and Access.

b) Data Redundancy

c) Data Dependence

d) Data Inconsistent

e) Data Isolation

f) Security

g) Integrity

h) Atomocity

i) Concurrent Access

Advantages of DBMS: a) No redundant Data

b) Data Consistency and Integerity

c) Secure

d) Privacy

e) Easy to access

f) Easy to recover

g) Flexible

2) Responsibilities of DBMS: a) Security enforcement: Unauthorized users can acces DB, or users authorized to access a part may acces other parts of DB for ehich their is a lack of authirization. For example an high school student could get access defence secrets, or employees can find what their supervisors earn.

b) Integri ty enforcement: Consistency constraints may not satisfied, a/c balances could go below theminimum allowed, employee may earn too much overtime, airline pilots may fly more hours than allowed.

c) Concurrency Control: Consistency constraints may be violated despite proper integrity enforcement in each transaction. For example, incorrect bank balances might be reflected due to simultaneous withdrawls and deposits.

3) A Primary key is one of the candiate keys, designed by database designer.

A candiate key is a minimal super key - a super key with no redundant attributes. In other words, if any one of the attributes are removed, the set of attributes that remain no longer form a super key.

A super is a set of attributes such that the values of the attributes uniquely identify one entity in the entity set.

Every primary key is a candiate key, every candiate key is a super key, but not vice-versa.

for example: consider a relation R(A,B,C,D,E) with 5 attribues A,B,C,D,E

A->BCDE, means A uniquely determines the other attributes B,C,D,E

BC->ADE, means B and C jointly determines all the other attributes A,D,E

Primary Key: A Candiate Key: A, BC Super Key: A, BC, ABC, AD
ABC and AD are that candiate keys since both are not minimal super keys,

4) a) _{loan_number} ( _{amount>50,000} (loan))

b) _{customer-name} ( _{balance>“9000”} ( _{depositer.account-number = account.account-number}(account x depositor)))

c) _{customer-name} ( _{balance>“8000” and branch-name=“Uptown”} ( _{depositer.account-number = account.account- number}(account x depositer)))