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mysqlsqlpostgresqlentitydifference

Why normal entity which dependents to parent table is can not named weak entity?

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There is one parent table "region". And weakentity is table "hospital" create table hospital( name varchar(32) id int, FOREIGN KEY(id) REFERENCES region (id),PRIMARY KEY(name,id),

and normal entity which dependents to region "hosp" create table hosp (name varchar(32), id int, r_id int, FOREIGN KEY (r_id) REFERENCES region(id), PRIMARY KEY(id)

Solution

  • No in your case weak entity is hospital and hosp because dependent to region Firstly understand about weak entity and normal entity 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. and normal entity is a thing, person, place, unit, object or any item about which the data should be captured and stored in the form of properties, workflow and tables. While workflow and tables are optional for database entity, properties are required (because entity without properties is not an entity)