CODEWITHSUNDEEP
databasedatabase-designentity-relationshiprelation
aakpro
aakpro

Reputation: 1578

Can a relation has a relation with another relation

can we have some thing like following ER?enter image description here

Is it a technical fault or not?

Upvotes: 3

Views: 752

Answers (1)

SSP
SSP

Reputation: 2670

To define a relationship there should be entity by the help of them you can show relation. so it is impossible to make relation without entity.

In your case if you want to use 2 relationship there should be 1 entity between them.

Example of real life

suppose you have two relation teacher and student. you can not say like i am teacher and student of XYZ.

But you can say like i am teacher of Xyz and student of abc.

Typr of relationship

One-to-many relationships

The most common relationship used when creating relational databases. A row in a table in a database can be associated with one or (likely) more rows in another table. An example of a one-to-many relationship is a single order has many items on that order. And since relationships work both ways it is not uncommon to hear reference to many-to-one-relationships as well.

One-to-one relationship

A row in a table is associated to one and only one row in another table. An example of a one-to-one relationship is a person can have one social security number and a social security number can only be assigned to one person.

In most cases there is no need for a one-to-one relationship as the contents of the two tables can be combined into one table.

Many-to-many relationships

When one or more rows in a table are associated with one or more rows in another table. An example of a many-to-many relationship is a table of customers who can purchase many different products and a table of products that can be purchased by many different customers.

Upvotes: 3

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