Dependency theory is a macro-level theoretical perspective concerned with questions of extreme disparities between modern nations. How do we account for such disparities (income, standard of living, etc.) between nations? The dependency theorists argue that the current economic and political arrangements...
Let supposeT (k)with the set of attributeskbe a relation scheme. Subsequently, we will represent subsets ofkasA,B,C. The standard notation in database theory for the set of attributes isABrather thanA∪B. Axiom of Reflexivity: If a set of attributes is P and its subset isQ, thenPhold...
Functional Dependency (abbreviated as FD below) is a traditional relation concept with a history as long as database itself. In relational database theory, a functional dependency is a constraint between two sets of attributes in a relation from a database. In other words, a functional dependenc...
2.Within the category of function dependency, the theory and application of normalization of relation model were studied.在函数依赖的范畴内对关系模型的规范化理论及其运用问题进行了研究 ,证明了关于Boyce- Codd( BC)范式两个定义的等价性 ,提出了关于 BC范式的一个实用的判定定理并加以证明 。 3.Within ...
the model were taken from natural language. The use of logical and Boolean operators was taken from mathematics. Data typing, domain specification and integrity maintenance were derived from computer programming language. Other remaining elements of the model were derived from general semantic theory. ...
Fundamentals of dependency theory 5.1 Introduction A database management system (DBMS) is essentially a computer system containing a large permanent store of data, with special routines and procedures for handling that data. As such systems evolved over the years, certai... MY Vardi 被引量: 125...
Dependency theory is a school of thought in contemporary social science which seeks to contribute to an understanding of underdevelopment, an analysis of its causes, and to a lesser extent, paths toward overcoming it. It arose in Latin America in the 1960s, became influential in academic circles...
A foreign key occurs when the columns of a primary key of a first table are present in a second table. Many of the commercial database management systems (DBMS's) of today are based on the relational database model. Examples of such systems are Oracle, DB2, Sybase, MS SQL Server, and...
Fundamentals of dependency theory 5.1 Introduction A database management system (DBMS) is essentially a computer system containing a large permanent store of data, with special routines and procedures for handling that data. As such systems evolved over the years, certai... MY Vardi 被引量: 125...
Fundamentals of dependency theory 5.1 Introduction A database management system (DBMS) is essentially a computer system containing a large permanent store of data, with special routines and procedures for handling that data. As such systems evolved over the years, certai... MY Vardi 被引量: 125...