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SQL
SQL (/ˌɛsˌkjuːˈɛl/ (About this soundlisten) S-Q-L,[4] /ˈsiːkwəl/ "sequel"; Structured Query Language)[5] is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). It is particularly useful in handling structured data, i.e. data incorporating relations among entities and variables.
SQL offers two main advantages over older read–write APIs such as ISAM or VSAM. Firstly, it introduced the concept of accessing many records with one single command. Secondly, it eliminates the need to specify how to reach a record, e.g. with or without an index.
Originally based upon relational algebra and tuple relational calculus, SQL consists of many types of statements,[6] which may be informally classed as sublanguages, commonly: a data query language (DQL),[a] a data definition language (DDL),[b] a data control language (DCL), and a data manipulation language (DML).[c][7] The scope of SQL includes data query, data manipulation (insert, update and delete), data definition (schema creation and modification), and data access control. Although SQL is essentially a declarative language (4GL), it also includes procedural elements.
SQL was one of the first commercial languages to use Edgar F. Codd’s relational model. The model was described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks".[8] Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database language.[9][10]
SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987.[11] Since then, the standard has been revised to include a larger set of features. Despite the existence of standards, most SQL code requires at least some changes before being ported to different database systems.
Mansfield is a market town in Nottinghamshire, England, the main town in the District of Mansfield and Mansfield Urban Area.[1] Mansfield gained the Royal Charter of a market town in 1227. The town lies in the Maun Valley, 12 miles (19 km) north of Nottingham, and is near Sutton-in-Ashfield. Most of the 106,556 population live within the town proper (including Mansfield Woodhouse), with Market Warsop as a secondary centre.[2] It is the only local authority in Nottinghamshire directly to elect its mayor.
