关系模型(国外英语资料).docVIP

关系模型(国外英语资料) Animation, tween, shape, inter frame, key frame, blank key frame A+ electronic version of the final release password Zhejiang Education Technology Center (/) website Access 2012 examination guidance 2011 examination guidance Select sort FLash original control Flow chart Check the answers of ten schools in Ruian Multimedia creation phase osi model Two hundred and thirty thousand eight hundred and three trillion and one hundred and ninety-eight billion nine hundred and two million two hundred and sixty thousand eight hundred and forty Boy 200831057203a325 88ae1d2ada20 172163522556644 Pots and basins 200804031903a325 206a8a48a7ac 172163590040513 News page bar, know MP3 pictures, videos, encyclopedia Library Help set Home page, natural, cultural, geographical, historical, social, artistic, character, economy, technology, sports pictures, digital museum, core user, encyclopedia store relational model medical aircraft A relationship is in fact the state or content of a pattern at a given moment. That is, the relational schema is type, and the relation is its value. Relational schema is static and stable, while relationships are dynamic and changing over time, because relational operations are constantly updating data in the database. But in practice, relationships, patterns and relationships are often referred to as relationships, and readers can be distinguished from context. Catalog brief introduction Description of relationships, patterns, and relationships Composition of relational model The basic terminology of a two-dimensional table brief introduction The relational model was proposed by E.F.Codd in 1970. Compared with the hierarchical mesh model, it has the following characteristics: 1. data structure is simple (two-dimensional table) 2. solid theoretical foundation. A. relational computing theory B. relational schema design theory Definition Relational model: a data model representing the relations between entities and entities in the form of a two-d