8. SQL

The Structured Query Language (SQL) is a language for working with information that has been stored in a database. SQL has three parts: the Data Manipulation Language (DML) concerns adding information to a database, modifying the information, and extracting information from a database; the Data Definition Language (DDL) is concerned with the structure of a database (creating tables); and the Data Control Language (DCL) is concerned with administration of a database (deciding who gets what sort of access to which parts of the database). This chapter is mostly focused on the SELECT command, which is the part of the DML that is used to extract information from a database, but other useful SQL commands are also mentioned briefly in Section 8.3.


Paul Murrell

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