A strong entity is any powerful force or presence, whether it is meant to mean some sort of deity, a high power such as a government or a business, or even an individual or group, etc.
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.
An entity set may not have sufficient attributes to form a primary key is called weak entity set. One with primary key is called strong entity set.
Entity instance is a single occurrence of an entity type. Also known as an instance. Unlike entity type, many instances of entity type may be represented by data stored in the database.
Entity Type : A collection of entities that share common properties or characteristics. for example student is an entity type with common attributes such as student_ID , Name, Class etc. These characteristics are common to all students. Entity Instance: A single occurrence of a particular entity type is called entity instance..
A weak entity can be identified uniquely only by considering the primary key of another (owner) entity.
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.
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.
an entity with reports
viable entity
an entity with reports
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 force
A strong democratic tradition can be surmised to mean that a nation or other entity has consistently enforced the ability of it's citizens or representatives to vote. The more democratic, the stronger the democratic process is.
An entity set may not have sufficient attributes to form a primary key is called weak entity set. One with primary key is called strong entity set.