0 votes 0 votes I think it should be option a) All query $1,3,4$ are equivalent but $2$ is not equivalent. Query $2$ should be $\prod \text{Room no,hotel no,type,price}(\sigma \text{type='single' } \wedge \text{price=200 })$ Databases relational-algebra relational-calculus + – Anand. asked Aug 17, 2018 Anand. 656 views answer comment Share Follow See 1 comment See all 1 1 comment reply Shubhgupta commented Aug 17, 2018 reply Follow Share Why? query 2 is also equivalent. It will print all rows of data with condition given. 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes When you don't use project and do only select, by default all the columns are returned, thus making Query 2 same as Query 1. Eg: goxul answered Aug 17, 2018 goxul comment Share Follow See all 3 Comments See all 3 3 Comments reply arvin commented Aug 17, 2018 reply Follow Share can u refer any link for that ? @goxul 0 votes 0 votes goxul commented Aug 17, 2018 reply Follow Share @arvin Sure, here you go. http://infolab.stanford.edu/~ullman/fcdb/aut07/slides/ra.pdf From Jeffrey Ullman's DBMS slides. You can find all of them here: http://infolab.stanford.edu/~ullman/fcdb/aut07/ 1 votes 1 votes arvin commented Aug 17, 2018 reply Follow Share thanks bro :) 0 votes 0 votes Please log in or register to add a comment.