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QUEL is a relational database query language, based on tuple relational calculus, with some similarities to SQL. It was created as a part of the Ingres DBMS effort at University of California, Berkeley, based on Codd 's earlier suggested but not implemented Data Sub-Language ALPHA. QUEL was used for a short time in most products based on the ...
The relational model ( RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, [ 1][ 2] where all data is represented in terms of tuples, grouped into relations. A database organized in terms of the relational model is a ...
Relational databases represent all relationships between data in an implicit manner only. [3] [4] For example, the relationships between customers and products (stored in two content-tables and connected with an additional link-table) only come into existence in a query statement (SQL in the case of relational databases) written by a developer.
In computing, online analytical processing, or OLAP ( / ˈoʊlæp / ), is an approach to quickly answer multi-dimensional analytical (MDA) queries. [ 1] The term OLAP was created as a slight modification of the traditional database term online transaction processing (OLTP). [ 2] OLAP is part of the broader category of business intelligence ...
Query language. A query language, also known as data query language or database query language ( DQL ), is a computer language used to make queries in databases and information systems. In database systems, query languages rely on strict theory to retrieve information. [ 1] A well known example is the Structured Query Language (SQL).
First normal form ( 1NF) is a property of a relation in a relational database. A relation is in first normal form if and only if no attribute domain has relations as elements. [ 1] Or more informally, that no table column can have tables as values. Database normalization is the process of representing a database in terms of relations in ...
The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database. [citation needed] These integrity constraints ensure compatibility between parts of the schema. All constraints are expressible in the same language. A database can be considered a structure in realization of the ...
The third normal form (3NF) is a normal form used in database normalization. 3NF was originally defined by E. F. Codd in 1971. [ 2] Codd's definition states that a table is in 3NF if and only if both of the following conditions hold: The relation R (table) is in second normal form (2NF). No non-prime attribute of R is transitively dependent on ...