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Question

Recursive relation require new table ?or not when we converting ER to relation?please explain

Answer 1

Suppose an instance of this relationship in database where,

UID - $102$ has $2$ Friends $\{103 \ 104 \}$

Now if you try to map this instance to single table maintaining the integrity which looks like this :
 

User.UID	User.Name	Friend.Uid(Foreign key)
102	a	??

You can`t map anything because there will be redundancy and database will not allow that rather :
 

user.UID	user.Name
102	a
103	b
104	c

friend.UID1	friend.UID2
102	103
102	104

Allowed and accepted and can be identified by combining both of these column. 

Comments

means two attributes are required in friend relation .?

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Relationships either recursive or non recursive are always meant for two entities or tables if you could do it with one attribute then its not a relationship anymore.