Looking at the Development of SQL

SQL was created because, early in the 1970s, IBM wanted a method with which nonprogrammers could extract and display the information they wanted from a database. Languages that nonprogrammers can use are called fourth generation, or 4GL, and sometimes are referred to as structured English. The first commercial result of this effort was Query By Example (QBE), developed at IBM's laboratories in Yorktown Heights, New York. QBE was used, beginning in the late 1970s, on terminals connected to IBM System 370 mainframes. A user could obtain a result with less than an 80-character line of QBE code that required 100 or more lines to implement in COBOL or the other 3GL languages of the day. Access, dBASE IV and 5, and Paradox use QBE to display selected data from tables.

At the other end of the country, programmers at IBM's San Jose, California facility were developing System R, the progenitor of SQL/DS and IBM's DB2 relational database. In the mid-1970s, IBM scientist Dr. E.F. Codd proposed SQL (then known as SEQUEL for Structured English Query Language) as a means of accessing information from the relational database model he had developed in 1970. Relational databases based on the Codd model that use the SQL language to retrieve and update data within them have become, like QBE, computer-industry standards.

SQL has achieved the status of being the exclusive language of relational client/server databases. A database server application (the back end) holds the data. Client applications (front ends) add to or edit the data. The client application generates SQL statements. If you deal regularly with databases of any type, the odds are great that you ultimately will need to learn SQL. You need to learn Jet SQL now if you plan to create applications with user-defined queries that work with the runtime version of Access. You also need to learn SQL if you want to take full advantage of the Internet Database Connector (IDC/HTX files) described in Chapter 18, "Creating Dynamic Web Pages."