30 votes 30 votes Which of the following relational query languages have the same expressive power? Relational algebra Tuple relational calculus restricted to safe expressions Domain relational calculus restricted to safe expressions II and III only I and II only I and III only I, II and III Databases gateit-2006 databases relational-algebra relational-calculus easy + – Ishrat Jahan asked Oct 31, 2014 Ishrat Jahan 9.1k views answer comment Share Follow See all 3 Comments See all 3 3 Comments reply set2018 commented Jul 25, 2017 reply Follow Share what is the meaning of "restricted to safe expressions" ? @Bikram sir 1 votes 1 votes Bikram commented Jul 25, 2017 reply Follow Share @ set2018 A safe expression means an expression which must always produce a finite number of tuples as its result . see these for example : http://people.cs.pitt.edu/~chang/156/10calculus.html http://www.w3schools.in/dbms/relational-calculus/ 4 votes 4 votes Deepak Poonia commented Nov 13, 2023 reply Follow Share Video Solution: https://youtu.be/mol0Mu5nBpA 1 votes 1 votes Please log in or register to add a comment.
Best answer 27 votes 27 votes Answer: D All are equivalent in expressive power. Rajarshi Sarkar answered Apr 12, 2015 • selected May 5, 2015 by Rajarshi Sarkar Rajarshi Sarkar comment Share Follow See all 8 Comments See all 8 8 Comments reply amkrj commented May 5, 2015 reply Follow Share what is the usage of " restricted to safe expressions" in the above question. Without it r there any difference? 3 votes 3 votes Rajarshi Sarkar commented May 5, 2015 reply Follow Share A safe expression yields a finite number of tuples as its result. Otherwise, it is called unsafe. 12 votes 12 votes Radha mohan commented Jul 1, 2018 i edited by Radha mohan Jul 1, 2018 reply Follow Share unsafe expressions can result in infinite number of tuples(a type of bug) and relational algebra doesn't give infinite number of tuples as result.Morever every unsafe expressions can be written in form of equivalent safe expression by restricting the domain of the resultant tuple to te database relations. 0 votes 0 votes ankitgupta.1729 commented Nov 5, 2018 reply Follow Share @Radha mohan , can you please explain or provide any reference for the statement "every unsafe expressions can be written in form of equivalent safe expression by restricting the domain of the resultant tuple to the database relations." ? 1 votes 1 votes Subinoy Manna commented Nov 21, 2018 reply Follow Share @Rajarsi Sarkar.can you please give an example of unsafe DRC expression? 0 votes 0 votes Verma Ashish commented Nov 23, 2019 reply Follow Share What if "restricted to safe expressions" is not given in question ?? 0 votes 0 votes srestha commented Dec 11, 2019 reply Follow Share Then all have different expressive power 0 votes 0 votes shashankrustagi commented Dec 5, 2020 reply Follow Share Any proof, please share. 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes 3 of them have same expressive power Bhagirathi answered Jan 15, 2015 Bhagirathi comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Relation algebra, tuple calculus and domain calculus are same in power. Akshada Shinde answered Nov 19, 2017 Akshada Shinde comment Share Follow See 1 comment See all 1 1 comment reply hitesh kumar kodopi commented Jun 24, 2021 reply Follow Share Relation algebra, safe tuple relational calculus and safe domain relational calculus are same in power.. so option D is correct. 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes Relational algebra has same expressive power as relational calculus (tuple relational calculus and domain relational calculus) and these all are relational query languages. so option D is true 1gate_cracker answered Nov 27, 2017 1gate_cracker comment Share Follow See all 0 reply Please log in or register to add a comment.