SQL was first defined in 1974 at the IBM Research Laboratory in San Jose, California. A prototype implementation was built there under the name “System R.” Successful testing results led to IBM’s decision to build products based on the System R technology. A number of other vendors also produced systems that support SQL.
Currently SQL has become the de facto standard for manipulating databases. It is used by most relational database systems. An official ISO/ANSI standard has been defined.
SQL is a standard language. Some vendors have created syntax that is not supported in any other environment to enable access to vendor specific features. For the larger part however, SQL is portable across database systems.
The SQL language defines statements to define and manipulate data. Using SQL, you can create a database, populate it and run reports on the data. We will take a quick look at the data manipulation statements. These allow you to select data, create new data, update existing data or delete data. The SQL statements for these actions are: select, insert, update and delete.
In our discussion of the SQL language, we will not go into detail. The purpose of this introduction is to show basic SQL constructs. It is not meant to be a complete discussion of the SQL language. Details are discussed in your database’s documentation; please refer to it for more information.
In our discussion of SQL statements, we will use the DataFlex Order Entry sample application sample data. For a discussion of this database, refer to Appendix A – The Order Entry Sample Application.
The discussion of SQL statements is in no way complete. We merely “scratch the surface” of the data manipulation statements. The data definition statements are not discussed at all. The purpose of this introduction is not to explain SQL to its fullest detail. It is intended to be a minimal overview of the SQL language.