What is an entity in database design
The Basic concepts of data modeling can be divided into Database fundamentals terms and the Computer science.To the Explanation of terms To get even closer to the topic of databases, the Terms in the conceptual database design and then the Designations in brackets listed for the physical database design.
Especially with the transfer from conceptual database design, about the logical database design into the physical database design problems can arise again and again. Hence be Methods how Bottom up or Top down used to this Eliminate problems.
Data modeling - basics and terms
Entity (table name): An entity represents an object of a subject area, which contains elements with the same characteristics. Examples of possible entities are: company, student, course and professor.
Entity set (all records of an entity): An entity set represents all data records that belong to an entity.
Relation (table): A relation comprises an entity including the associated entity set. A complete relation consists of an entity name, its attributes and tuples.
Important note on the term relation and table:
Nowadays the terms relation and table are equated. Unfortunately, this is very problematic because the word “relation” means “relationship” in English. A relationship, however, has a completely different meaning in the database fundamentals and states the relationship between two tables.
Tuple (data set): A tuple represents all characteristic values of an entity of an entity set. All tuples of an entity form the entity set.
Attribute (column name): An attribute describes exactly one characteristic of a tuple in an entity set, for example the name of a customer.
Attribute value (value): The attribute value represents the value that an attribute can assume in a tuple, for example: Attribute => Name = "Meier" <= Attribute value
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