0 votes 0 votes How many minimum tables are required for this er diagram consisting of a many - many relation and total participation of one of the entities.? Can't i merge relation R and entity B? why? Databases gatebook-dbms databases er-to-relational relations + – aditya kuppa 1 asked Dec 5, 2017 retagged Dec 5, 2017 by aditya kuppa 1 aditya kuppa 1 1.0k views answer comment Share Follow See all 7 Comments See all 7 7 Comments reply Show 4 previous comments vamp_vaibhav commented Dec 6, 2017 reply Follow Share You can't merge these two entities.. Even at minimum we require three tables to represent this relationship.. Reason is that : suppose you have relationship(works on) and first entity as employee and second entity as project. Now if we have many to many relationship then one employee can participate in many relationship and one project can also participate in many relationship If you try to merge two entities in one table you will have table like an employee A works on project 1,2,3 and so on but in each column we can't represent more than one value. And empid is unique.. Therefore we make two separate table for two entities and the primary key of both entities are stored in another separate table 1 votes 1 votes aditya kuppa 1 commented Dec 6, 2017 reply Follow Share But cant we have different tuples of A mapped with each project in the merged relation.? My root of the doubt is like this, suppose if both the entities have total participation and d relationship is many to many we can combine all into one . Same could be applied here right. 0 votes 0 votes twin_123 commented Aug 29, 2018 reply Follow Share So ashwin number of table is 3 right? 0 votes 0 votes Please log in or register to add a comment.
2 votes 2 votes There will b 3 tables. Since for M to M relation, there will b seperate table for the relation R.Therefore One for A, second for B and third for R. Plse do correct me if i am worng.Thankyou! Yash_Pandey answered Feb 23, 2018 Yash_Pandey comment Share Follow See 1 comment See all 1 1 comment reply Gurdeep Saini commented Aug 24, 2018 reply Follow Share Yes @yes panday And the prime key of relation table is the combination of primary key of table A and table B 0 votes 0 votes Please log in or register to add a comment.