dependents in an organization
why do we need weak entity in database when we can make it strong 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.
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.
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.
Sure thing, honey. An identifying relationship of a weak entity type can definitely have a degree greater than two. For example, let's say we have a weak entity type called "Order Item" that depends on both "Order" and "Product" entities to uniquely identify it. In this case, the identifying relationship would have a degree of two (connecting "Order" and "Product") but the weak entity type itself would have a degree of three. Hope that clears things up for ya!
Weak entity means an entity which doesnt uniquely exist and requires another foreign entity for its complete representation. For example, we have a University database and we have a table of departments having dept_id as its primary key. Now, a department cannot exist independently unless there is a university, so this entity needs university id as well to represent it.
an entity set may not have sufficient attribute 2 form a primary key is called weak entity set.ex entity set payment has 3 attribute pay-no,pay-date, pay-amount.pay-no is a sequential no generated 4 each loan.each payment entity is distinct,payments 4 different loans may share the same payment no.thus entity set doent have a primary key,so it is a weak entity set. Placid04 bakhra,muzaffarpur,bihar.
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.
A weak entity can be identified uniquely only by considering the primary key of another (owner) entity.
weak entity
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.
The table that has primary key is strong entity and the table that has no primary key is weak entity