Relational Model :: essays research papers

The Relational Database ModelA database discharge be understood as a prayer of tie in files. How those files argon related depends on the cast used. Early models included the hierarchical model (where files are related in a parent/ minor manner, with each child file having at most one parent file), and the network model (where files are related as owners and members, similar to the network model besides that each member file can have more than one owner). The relational database model was a huge step forward, as it allowed files to be related by means of a common country. In enjoin to relate any two files, they simply need to have a common field, which makes the model extremely flexible.Poet Code First Name designation Age 1 Mongane Afrika 62 2 Stephen Serote 58 3 Tatumkhulu Watson 29 Poem Title Poet Wakening Night 1 Thrones of Darkness 2 Once 3 These two tables relate through the code field in the poet table, and the poet field in the metrical composition table. We can se e who wrote the poem Once by following the relationship, and see that it was poet 3, or Tatumkhulu Watson.In 1970, when E.F. Codd developed the model, it was horizon to be hopelessly impractical, as the machines of the time could not cope with the hit necessary to maintain the model. Of course, hardware since then has come on in huge strides, so that today even the most basic of PCs can run sophisticated relational database management systems. Together with this went the development of SQL. SQL is relatively easy to learn and allows people to quickly learn how to perform queries on a relational database. This simplicity is part of the reason that relational databases outright form the majority of databases to be found. Basic TermsAn understanding of relational databases requires an understanding of some of the basic terms. Data are the values stored in the database. On its own, data means very little. "43156" is an framework. Information is data that is svelte to have a meaning. For example, "43156" is the population of the town of Littlewood. A database is a collection of tables. Each table contains records, which are the horizontal rows in the table. These are besides called tuples. Each record contains fields, which are the vertical columns of the table. These are also called attributes. An example would be a product record.