An entity set that does not possess sufficient attributes to form a primary key is called a weak entity set. One that does have a primary key is called a strong entity set.
The discriminator (or partial key) of a weak entity set is the set of attributes that distinguishes among all the entities of a weak entity set
The existence of a weak entity set depends on the existence of a identifying entity set. It must relate to the identifying entity set via a total, one-to-many relationship set from the identifying to the weak entity set
We depict a weak entity set by double rectangles in E-R diagram. We underline the discriminator of a weak entity set with a dashed line in E-R diagram.
strong entity is the entity that can stand alone
weak entity cannot be exist alone.
usually strong entity represent an real world entity such as course , student, patient, ward, department, employee,.... etc
but
the weak entity represents the relationship between two entities, so in connot be exist alone, there must be two strong entities that the weak entity will connect.
strong entity : in this the attributes must have values for instance . weak entity : in this the attributes may or may not have values for instance .
What is the difference between strong and brave
the enitity which is set primary key is said to be strong entity and the entity which does not set primary key is said to be weak entity.
A weak entity set can always be make into strong entity set by adding to its attribute of its identifying entity set. For a weak entity set, we add columns to the table corresponding to the primary key of the strong entity set on which the weak set is dependent.
there is no differences between strength and strong. Only that strong is a synonym of strength.
why do we need weak entity in database when we can make it strong entity?
The table that has primary key is strong entity and the table that has no primary key is weak entity
The primary key of a weak entity set is formed by taking the primary key of the strong entity set on which its existence depends (see Mapping Constraints) plus its discriminator. A strong entity set has a primary key. All tuples in the set are distinguishable by that key. A weak entity set has no primary key unless attributes of the strong entity set on which it depends are included. Tuples (a particular row) in a weak entity set are partitioned according to their relationship with tuples in a strong entity set. Tuples within each partition are distinguishable by a discriminator, which is a set of attributes.
Nationalism involves a strong identification of a group of individuals with a political entity defined in national terms, i.e. a nation. Often, it is the belief that an ethnic group has a right to statehood.
strong
what is the answer
strong force