0 votes 0 votes Question: If we have two relation R(A,B,C) and S(D,E,F),where A and D are primary key and attribute C is working as Foreign key and referring to D.So is it possible to C have NULL in some rows?? Reference:: https://gateoverflow.in/2151/Gate-cse-2012-question-43?state=showcomments-2377&show=2377#a2377 Databases self-doubt relational-algebra databases + – lalitver10 asked Apr 8, 2022 lalitver10 283 views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply shishir__roy commented Apr 8, 2022 i edited by shishir__roy Apr 8, 2022 reply Follow Share https://www.geeksforgeeks.org/constraints-on-relational-database-model/amp/ https://en.m.wikipedia.org/wiki/Referential_integrity C can take either null values or some value of D. The only restriction is that C should not take any value which is not equal to some row value of D. 0 votes 0 votes lalitver10 commented Apr 8, 2022 reply Follow Share Hii @shishir__roy Thanks for reply.can you please share some valid document related to this if you have. 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes Yes it is possible for C have NULL in some rows. Foreign key value can be either NULL or some value from referenced Attribute D. aaaakash001 answered Oct 15, 2022 aaaakash001 comment Share Follow See all 0 reply Please log in or register to add a comment.
