<Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2008) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2008) (Learn how and when to remove this template message) </Td> </Tr> <P> In a relational database, a weak entity is an entity that cannot be uniquely identified by its attributes alone; therefore, it must use a foreign key in conjunction with its attributes to create a primary key . The foreign key is typically a primary key of an entity it is related to . </P> <P> In entity relationship diagrams, ER diagrams a weak entity set is indicated by a bold (or double - lined) rectangle (the entity) connected by a bold (or double - lined) type arrow to a bold (or double - lined) diamond (the relationship). This type of relationship is called an identifying relationship and in IDEF1X notation it is represented by an oval entity rather than a square entity for base tables . An identifying relationship is one where the primary key is populated to the child weak entity as a primary key in that entity . </P>

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