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A one-to-many relationship is not a property of the data, but rather of the relationship itself. One-to-many often refer to a primary key to foreign key relationship between two tables, where the record in the first table can relate to multiple records in the second table. A foreign key is one side of the relationship that shows a row or ...
The entity–relationship model proposes a technique that produces entity–relationship diagrams (ERDs), which can be employed to capture information about data model entity types, relationships and cardinality. A Crow's foot shows a one-to-many relationship. Alternatively a single line represents a one-to-one relationship. [4]
Base One Foundation Component Library, free or commercial; Dapper, open source; Entity Framework, included in .NET Framework 3.5 SP1 and above; iBATIS, free open source, maintained by ASF but now inactive. LINQ to SQL, included in .NET Framework 3.5; NHibernate, open source; nHydrate, open source; Quick Objects, free or commercial
Object–relational mapping (ORM, O/RM, and O/R mapping tool) in computer science is a programming technique for converting data between a relational database and the memory (usually the heap) of an object-oriented programming language. This creates, in effect, a virtual object database that can be used from within the programming language.
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
Relationships provide directed, named, semantically-relevant connections between two node entities. A relationship always has a direction, a start node, an end node, and exactly one relationship type. Like nodes, relationships can also have properties. [4] Labels can group similar nodes together by assigning zero or more node labels.
One-to-many (data model), a type of relationship and cardinality in systems analysis; Point-to-multipoint communication, communication which has a one-to-many relationship; A one to many relation, a relation such that at least one element of its domain is assigned to more than one elements of its codomain, and no element of its codomain is ...
The following example represents an n-to-1 relationship between movies and their directors. It is shown how user-defined Python classes create corresponding database tables, how instances with relationships are created from either side of the relationship, and finally how the data can be queried — illustrating automatically generated SQL ...