What is SQL?

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by Jason Earls, 17 January 2008    (for ALL VERSIONS of Access)

SQL is an acronym that stands for “Structured Query Language” and is most commonly pronounced like the word “sequel.” SQL was first created by IBM in the 1970s and due to its popularity is now considered the standard language for retrieving and editing data stored in relational databases on various networks of the client-server type. SQL was fully standardized by ANSI/ISO in 1987.

SQL uses four main commands for querying data: UPDATE, SELECT, INSERT, and DELETE. These basic commands relate to the four main functions of manipulating any type of data. The SELECT command serves to retrieve data; the UPDATE command modifies data; the DELETE command erases data; and the INSERT command incorporates new data.

The queries (search questions requesting data) used in SQL closely resemble the basic format of a natural human language, such as French or Spanish. However, SQL is not a general purpose language like Fortran or C, but a declarative language used only to describe a problem rather than give a solution. SQL is specific for querying databases and only works on sets of objects, while C and Fortran were made to solve a much wider range of problems. The results of a query in SQL are usually listed in tables and made up of simple rows and columns.

Common criticisms of the SQL language are that it violates the common logic that should underlie all relational databases, which was formulated and proposed by Edgar Codd in 1969. Also, people complain that the compatibility of the SQL language from vendor to vendor is not consistent. For example, case sensitivity, use of nulls, and syntax of date and time are often different from one SQL implementation to another.

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