Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Define the basic operations of the relational algebra?
Ans: Basic operators of relational algebra are:
1. Union (∪) - Selects tuples which are in either P or Q or in both of them. The duplicate tuples are removed.
R = P ∪ Q
2. Difference or Minus (-) - eliminates common tuples from the first relation.
R = P - Q
3. Cartesian Product or Cross Product (×) - The cartesian product of two relations is the concatenation of tuples that are belonging to the two relations and containing all possible combination of the tuples.
R = P× Q
4. Projection (π) - The projection of a relation is illustrated as a projection of all its tuples over some set of attributes that is it yields a vertical subset of the relation. The relation's projection T on the attribute A is presented by T [A] or πA(T),.
5. Selection (σ) - Selects just some of the tuples, those satisfy specified criteria, from the relation. It yields a horizontal subset of a following relation.
R = σB(P)
Performance of Various Concurrency Control Mechanisms
Discuss the problem of Spurious tuples and how we may prevent it. Ans: A spurious tuple is, mainly, a record in a database that gets created while two tables are joined bad
Consider a database schema consisting of four relations, whose schemas are: Product (maker, model, type) PC (model, speed, ram, hd, price) Laptop (model, speed, ram, hd, s
What are the three classes of SQL expression? SQL expression consists of three clauses: Select From Where
When is UPDATE_STATISTICS command used? - When processing of large data is done, this command is used. - Whenever large number of modification, deletions or copy takes place
..
Example RELATION SCHEMA for STUDENT: STUDENT (Roll No: string, name: string, login: string, age: integer) RELATION INSTANCE
Run the following queries. For each query show 1) What you expect the output to be based upon the data 2) the SQL code and 3) the output running the query in Oracle. 1. Show all c
Consider the subsequent relations RENTER(rno, fname, lname, address, tel_no, pref_type, max_rent) VIEWING(rno, pno, date, comment) PROPERTY_FOR_RENT( pno, street, area ,city,
Task Part A. Create an ERD from a business problem. (50 marks) Read the following problem and complete the tasks listed below. THE ABS Blood Bank Australian Blood Services (ABS) i
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd