SQL
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SQL Tutorial - SQL Query Reference and Programming Examples
SQL (Structured Query Language) is a computer language aimed to store, manipulate, and query data stored in relational databases. The first incarnation of SQL appeared in 1974, when a group in IBM developed the first prototype of a relational database. The first commercial relational database was released by Relational Software (later becoming Oracle). Standards for SQL exist. However, the SQL that can be used on each one of the major RDBMS today is in different flavors.
Write down everything the application has to do, down to the last detail. If multiple apps will use the database, include everything that all the apps have to do. This first list needn't be organised by sequence or topic at this stage. It just has to be complete. Group the Elements from Step 2 into lists of attributes that belong together, so each list defines exactly one kind of thing that the app will have to deal with—a customer, a book, a widget &c—and no element is itself a list.
Basics of designing a database
Oracle