1 votes 1 votes help please how the eqyation 1 can be equivalent to text in red , as far as i know its wrong because to do set difference , they should be union compatible ??? plz reply sumit goyal 1 asked Jun 25, 2017 sumit goyal 1 280 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes u are right. First Equation is not true Abhisek Das answered Jun 25, 2017 Abhisek Das comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes if we subtract two relation then it must union compatable. means if r and s have two relation then the attribute(column) must be same of both relation. so in above example we cannot subtract abhishekmehta4u answered Jul 3, 2017 abhishekmehta4u comment Share Follow See all 0 reply Please log in or register to add a comment.