SQL (/ˌɛsˌkjuːˈɛl/ (About this soundlisten) S-Q-L, /ˈsiːkwəl/ "sequel"; Structured Query Language) 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, 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] 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". Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database language.
SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987. 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.
Market Harborough is a market town within the Harborough district of Leicestershire, England. It is situated in the far southeast of the county, forming part of the border with Northamptonshire.
Harborough District has a population of 91,461 (2017) and Market Harborough is the district's administrative headquarters. It sits on the Northamptonshire-Leicestershire border. The town was formerly at a crossroads for both road and rail; however the A6 now bypasses the town to the east and the A14 which carries east-west traffic is 6 miles (9.7 km) to the south. Market Harborough railway station is served by East Midlands Railway services on the Midland Main Line with direct services north to Leicester, Nottingham, Derby and Sheffield and south to London St Pancras. Rail services to Rugby and Peterborough ended in 1966.
Market Harborough is located in an area which was formerly a part of the Rockingham Forest, a royal hunting forest used by the medieval monarchs starting with William I. Rockingham Road takes its name from the forest. The forest's original boundaries stretched from Market Harborough through to Stamford and included the settlements at Corby, Kettering, Desborough, Rothwell, Thrapston and Oundle.
The steeple of St Dionysius' Church rises directly from the street, as there is no churchyard. It was constructed in grey stone in 1300 with the church itself a later building of about 1470. Next to the church stands the Old Grammar School, a small timber building dating from 1614. The ground floor is open, creating a covered market area and there is a single room on the first floor. It has become a symbol of the town. The nearby square is largely pedestrianised and surrounded by buildings of varying styles. The upper end of the High Street is wide and contains mostly unspoiled Georgian buildings.
Market Harborough has two villages within its confines: Great Bowden lies over a hill about a mile from the town centre; Little Bowden is less than half a mile from the town centre. The three centres have largely coalesced through ribbon development and infill, although Great Bowden continues to retain a strong village identity.