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Feb 7, 2011 · Basically, all types that the database system itself offers, like NUMERIC, VARCHAR etc., or that the programming language of choice offers (int, string etc.) would be considered "atomic" data (base) types. Anything that you - based on your program's or business' requirements - build from that, business objects and so forth, are entities.
Jul 9, 2016 · 1. What i know about weak entity is that they cannot exist without strong entity:-. i.e there must be a strong entity from which key (foreign key) has to be taken by weak entity. example : a HOTEL (strong entity) and ROOM (weak entity), HOTEL is strong entity because they can have their existence by their own (independently) while ROOM is weak ...
Dec 2, 2014 · 1.Degree. This is the number of entities involved in the relationship and it is usually 2 (binary relationship) however Unary and higher degree relationships can be exists. 2.Cardinality. This specifies the number of each entity that is involved in the relationship there are 3 types of cardinality for binary relationships. one to one (1:1)
Feb 16, 2019 · Entity Type: It is collection of entity having common attribute. Entity Instance: An entity instance is a single occurrence of an entity. So to clarify your confusion, entity is a more abstract or general way of referring to an entity instance or a type.And yes EMPLOYEE is an entity type. References: instance, entity, another answer with example.
2. What are some examples of user-defined integrity rules in a database system? It means setting up certain conditions for the columns and when data is inserted it needs to fulfill these conditions. For example: If I set up a rule that an ID needs to consist of 5 integers ONLY then when I insert a row with an ID which is made up of integers and ...
Mar 31, 2010 · 78. A class is a template for an object (among other things), and is a very general concept. An entity has more semantic significance and is usually tied to a concept (possibly about a real object for example, an Employee or a Student or a Music Album) and is linked to business logic. Entities are usually used to establish a mapping between an ...
Jan 20, 2011 · A weak entity is one that can only exist when owned by another one. For example: a ROOM can only exist in a BUILDING. On the other hand, a TIRE might be considered as a strong entity because it also can exist without being attached to a CAR. edited Jun 18, 2018 at 7:23. Heniam.
May 21, 2013 · 4. In an ER diagram, I believe when the relationship is strong, i.e., the primary_key of the parent forms a composite or non-composite primary_key in the child entities, we use a solid line to depict that. Similarly, for the case when the relationship is weak, which means the primary_key of the parent is not used as a primary_key in the child ...
Jan 29, 2020 · There is little difference between an entity and a table, but first we should define the concepts of “tuple” and “attribute”. I want to express those concepts with a table. Here is an example of a table. As you can see it has some columns. Each column represents an attribute and each line represents a tuple(row). This is the employee table.
Nov 14, 2013 · 24. Amazingly, "relation" in "relational" databases does not refer to the foreign key relationship of one table to another. "A relation is a data structure which consists of a heading and an unordered set of tuples which share the same type," according to Wikipedia on 'Relation (database)'. In SQL RDBMSes (such as MS SQL Server and Oracle ...
