#DBMS

Question

What are the parameters or procedure to follow to find out minimum no. of tables for given ER Diagram type of questions?

Comments

1) Individual table for each entity unless there is total participation from either end with 1:1 relationship, in such case we just need 1 table.

2) Individual table to address multivalued/composite attributes.

3) No table required, if the relation is 1:1 or 1:M or M:1, where as a seperate table is needed for the relation, if it's M:N.

4)  in 1:M relation,M sided attribute will have reference to the relation (M sided attribute will contain reference to the foreign key of 1 sided relation).

 

In case if i have missed something, pls comment..

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In 4th point you want to say that the attribute which is present on the relationship will be adjusted in the table with M side...??Is it so

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Yes..

Answer 1

1.Only Partial participations-

• One-One:2 Tables, Merge Relation to any of the side.
• Many-One or One-Many:2 Tables, Merge Relation to Many side.
• Many-Many:3 tables (separate table for relation)

2. Any one of the  side has full participation-

• Full participation on Many Side: 2 Tables
• Full Participation on one side: 1 Table

3.Both Side full participation-

• Always one table irrespective of Cardinality.