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Rather, they show entity sets (all entities of the same entity type) and relationship sets (all relationships of the same relationship type). For example, a particular song is an entity, the collection of all songs in a database is an entity set, the eaten relationship between a child and his lunch is a single relationship, and the set of all ...
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.
Thus, the "relation" in "relational database" refers to the various tables in the database; a relation is a set of tuples. The columns enumerate the various attributes of the entity (the employee's name, address or phone number, for example), and a row is an actual instance of the entity (a specific employee) that is represented by the relation.
An object database stores complex data and relationships between data directly, without mapping to relational rows and columns, and this makes them suitable for applications dealing with very complex data. [19] Objects have a many-to-many relationship and are accessed by the use of pointers. Pointers are linked to objects to establish ...
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
An object–relational database (ORD), or object–relational database management system (ORDBMS), is a database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language.
3. Related to money and/or monetary units. 4. All of the terms in this category precede a common three-letter noun (hint: the word typically refers to a small container that's used for drinking).
A relationship can be specified to take an Action when some Operation is done on a related entity. For example, on deleting an entity that forms the part of a relation (the OnDelete operation) the actions that can be taken are: [38] Cascade, which instructs to delete the relationship instance and all associated entity instances. None.