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Determine the Strong and Weak Entity
Based on the method of foreign key, there might be arise a situation when we have to relate an entity having a primary key of its own and an entity not having a primary key of its own. In such a case, the entity having its own primary key is known as a strong entity and the entity not having its own primary key is known as a weak entity. Whenever we need to relate a strong and a weak entity together, the ERD would alter just a little.
Say, for instance, we have a statement "A Student lives in a Home." STUDENT is obviously a strong entity having a primary key Roll. But HOME might not have a unique primary key, as its only attribute Address may be shared by a lot of homes (what if it is a housing estate?). HOME is a weak entity in this case.
What is a SELECT operation? The select operation selects tuples that please a given predicate. We use the lowercase letter σ to denote selection.
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#questiontypes of keys examples..
i want notes on this topic
What will be create when a primary key if combined with a foreign key? A primary key if combined with a foreign key it creates Parent-Child relationship between the tables that
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