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Structured Query Language (SQL)


The SQL Reference Guide is a multipart document designed to introduce the reader to the basics of SQL. In most Relational Database Management Systems [RDBMS] that use Structured Query Language [SQL] the following is the standard syntax. There are differences between SQL Server, MySQL, Oracle, PostgreSQL, and any other that might be in use. To keep the document consistent everything is written for SQL Server and examples from other database engines will be provided.


SQL Clauses

SQL has a few major clauses that are necessary in order to retrieve information from the database. Some of them are required others are optional. Every SQL query must contain a SELECT and a FROM clause. Everything else is optional however the WHERE clause is necessary to control what data will be returned from the query.