Q. Can Primary key is a Foreign Key on the same table? ~ SQL

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Q. Can Primary key is a Foreign Key on the same table?

Answer: Yes, Primary key can act as a Foreign Key on the same table.

For Example:-

CREATE TABLE T (

GroupID int not null,

ItemID int not null,

ParentItemID int null,

constraint PK_T PRIMARY KEY (GroupID,ItemID),

constraint FK_T_Parent FOREIGN KEY (GroupID,ParentItemID)

references T (GroupID,ItemID)

)