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!
How does a query tree represent a relational algebra expression? Discuss any three rules for query optimisation, giving example as to when should each rule be applied.
Ans: A query tree is a tree structure which refers to a relational algebra expression. It denotes the input relations as leaf nodes of the tree, and denotes the relational algebra operations as internal nodes. An execution of the query tree contains executing an internal node operation while its operands are available and after that replacing that internal node by the relation which results from executing the operation. The execution terminates while the root node is executed and generates the result relation for the query. For instance, the query tree for the relational algebra expression
∏E_No =(σp_No = 'DB2003' (Assigned_To) :
The three rules for query optimization are like this:
∏1(∏2(......∏n ( R))) ≡ ∏1(R )
∏A1, A2,......An (σC (R ) ≡ σC (∏A1, A2, ......An (R ))..... ))
σC1 AND C2 AND ....AND Cn (R ) ≡ σC1 (σC2(....(σCn (R ))....))
what is Mapping Constraints? with examples
What is the difference between SQL Server 2000 clustered and nonclustered indexes? With a clustered index, the data are kept in the bottom level of the index and in the similar
I want to buy this but I want to see a couple sample questions first. http://www.expertsmind.com/library/what-happens-to-rms-error-for-the-training-data-set-51564843.aspx
For problems 1-4, give all candidate keys for the tables with FDs specified. Composite candidate keys must be put in parentheses, and candidate keys must be separated with commas
QUESTION (a) Using an appropriate example, explain what is a recursive function? (b) Explain in detail the C++ function given below. void search2(int list[],int n,int ele
FitAll Ltd is a company that manufactures clothes. Its processes are manual and there are stand-alone Information Systems that aid to manage them. The Information Systems were purc
Which is a legal expression in SQL? SELECT NAME FROM EMPLOYEE is a legal expression in SQL.
Object Oriented model :An object has values stored in instance variables within the object. An object also has bodies of code that execute on the object. These bodies of code are
Suppose R is a relation with attributes A1, A2,..., An. As a function of n, tell how many superkeys R has, if: 1.1 The only key is A1. 1.2 The only key is A1 and A2. 1.3 The o
what is Lossless-join decomposition
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: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd