Entity-Relationship Model - Weak Entity Sets | Database Tutorial 3e
In this lecture of the databases course we learn about weak entity sets in the entity-relationship model (ER model). Weak entity sets are entity sets that do not have key themselves. They must have an identifying relationship set that relates every weak entity to precisely one identifying entity. The weak entities must have a so-called discriminator which is a partial key that identifies them in combination with the (key of) the corresponding identifying entity.
This is the databases online course given at the Vrije Universiteit Amsterdam by Jörg Endrullis. The course objective is to obtain a good understanding of relational database systems from the user perspective. This includes the ability to develop conceptual database models, as well as key concepts and skills in relational database theory and practice.
Among others, we treat in this course the following subjects:
(a) entity–relationship diagrams for the design of database schemata,
(b) the relational database model and integrity constraints,
(c) SQL (structured query language) for retrieving information from relational databases,
(d) database normalisation and functiona dependencies (reasoning about good database design),
(e) transactions and concurrency control.
The slides are based on work by Peter Boncz and Torsten Grust.
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