Disparate data can inhibit value creation, but data integration best practices allow organizations to fully leverage the inherent value in their information resources.
By John Gay
Silos of disparate data plague many companies. The reasons for the data diversity vary: organizations may run best-of-breed applications on the most appropriate platform for each product; in the days of client/server computing, the responsibility for choosing applications may have been decentralized, with different departments choosing different platforms; a merged company may use a variety of different applications, keeping separate some of the formerly individual companies' activities and the software that supports those parallel activities, while choosing the best of the predecessor companies' applications to serve those business functions that are merged. And the list goes on.
In SQL, the basic SELECT statement displays one or more columns from a single file. When columns must be merged from two or more files, a join should be used. There are two ways to accomplish this. A join can be written either with or without the JOIN keyword. Creating simple joins is easy enough, but as they get more complex, using the JOIN keyword becomes more attractive.