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Is primary key is the principle means of identifying entities within an entity set?
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∙ 10y ago
Yes
Wiki User
∙ 10y ago
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Can weak entity be converted into strong entity in DBMS?
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.
What is difference between object and entity?
A database object is represented as one of the following: database, schema, table, column, primary key, and foreign key A database Entity is: An entity is a thing or object of importance about which data must be captured. All things aren't entities - only those about which information should be captured. Information about an entity is captured in the form of attributes and/or relationships. If something is a candidate for being an entity and it has no attributes or relationships, it isn't an entity. Database entities appear in a data model as a box with a title. The title is the name of the entity.
What is entities database?
Entity means a specific thing in both database work and data modeling. An entity is data that can be classified, and has a relationship with other classified data, as in entities.
What is weak entity sets in dbms?
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 type vs entity instance?
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..
What is strong entities vs weak entities?
The table that has primary key is strong entity and the table that has no primary key is weak entity
Explain the difference between a weak and a strong entity set?
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.
Can weak entity be converted into strong 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.
Possessive form of the word entity?
Possessive: entity's Plural: entities Possessive plural: entities'
What is the plural of entity?
Entities.
Can weak entity be converted into strong entity in DBMS?
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.
What is a composite or bridge entity in database terms and when is it used?
it is an entity whose primary key is composed of the combination of the primary keys of the entities that must be linked. It is used in linking tables of the M:N relationship that needs to be converted into two 1:M relationship for your database
How is subtraction like adding?
Subtraction is nothing like addition. If you are talking about addition, it means that 1+1=2 - one entity + one entity = two entities. Entities=numbers. However, for subtraction it is the opposite. 1-1 = 0 - one entity eats/- one entity = zero entities. There are no other entities to eat except for itself. Thus when it eats itself, there are no more entities left.
Difference between specialization and generalization?
As the name implies, Generalization is going general. For example if you have entities like Medical-student, Engineering - student, Architecture - student so on, you can generalize and create an entity called Student (higher level entity) so others will be sub entities (lower level entities) of Student entity. One thing to keep in mind is that, the generalized entity is the union of all the sub entities, in the sense it will contain everything that is in its sub entities. This is Bottom Up approach! Specialization is about going specifically. For a given entity you create sub entities. For example if Staff entity is there, you create Maintenance staff, IT staff, Executive staff so on. Here the higher level entity (Employee) is given and we create the lower level entities. However unlike in Generalized entity, the higher level entity is NOT union of its lower level entities. Sub entities here will use some things from its higher level entity plus things on its own. This means that there could be things that's in lower level entities but not in higher level entity.
Which entity type depends is called identifying owner?
weak entity
What is difference between object and entity?
A database object is represented as one of the following: database, schema, table, column, primary key, and foreign key A database Entity is: An entity is a thing or object of importance about which data must be captured. All things aren't entities - only those about which information should be captured. Information about an entity is captured in the form of attributes and/or relationships. If something is a candidate for being an entity and it has no attributes or relationships, it isn't an entity. Database entities appear in a data model as a box with a title. The title is the name of the entity.
What is entity relationship diagrame?
An entity relationship diagram (ERD) represents the entities, or groups of information, and their relationships maintained for a business. An entity relationship diagram represents the entities, or groups of information, and their relationships maintained for a business. An entity relationship diagram represents the entities, or groups of information, and their relationships maintained for a business.
