Er model

Question

why we can merge one-one relation in two table despite of partial participation at both end.it is possible of inserting too many null value?

Comments

i think if its total participation we will have only one table. but if its partial we merge the one with more participation with the relation. and one with least participation become one single table.

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i think partial participation at both the ends is not possible. im not sure

and i didnt get your question.

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@daksirp, it is our requirement means our choice...

may be some one have that requirement...

@shubgol, if you are merge in one table, then what is the key of that table

Answer 1

If a one - one relation has a partial participation on both the sides then we have to create two tables because if we merge everything in just one table then, there might be a chance that null values be inserted in primary key and as the rule says null values are not allowed in primary key

But if we have total participation on both sides then we can have only one table.

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Comments

if we merge relation table with any one of entity table then also possible of null value in attribute except prime.so my doubt is null value is valid in relational table.
plz reply if u know