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)
Define Query by Example QBE is a query language relies upon domain calculus and has two dimensional syntax. The queries are written in the horizontal and vertical dimensions of
Eliminate Repeating Groups The problem is, "Find out the list of employees, who knows DB2". For this problem we require to perform an awkward scan of the list looking for re
Define Boyce codd normal form A relation schema R is in BCNF with respect to a set F of functional dependencies if, for all functional dependencies in F + of the form.α ->β.
Fifth Normal Form (5NF) These relations still have a difficulty. While defining the 4NF we mentioned that all the attributes depend upon each other. Whereas creating the two ta
What do you understand by a view? What does WITH CHECK OPTION clause for a view do? - A view is a virtual table which comprises fields from one or more real tables. - It is
Consider a database application that deals with an Employee relation with information such as SIN, name, data of birth (DOB), and DID (the ID of the department at which the employe
Designing the fields in the data base The following are the considerations one has to remain in mind while designing the fields in the data base. Coding, compression, en
What is the purpose of tables, private synonyms and public synonyms? If there are multiple objects of similar name on an Oracle database, that order are they accessed in? The r
Why do so various organizations use MySQL? Advantages: Open source Highly efficient Offers a high scalability in terms of size and connectivity. Highly prote
Describe about Use Case and external case in DFD The processes are transformed those into the Use Case and external case in DFD has same characteristics which of an actor in O
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