Knowra SQL SQL SQL is a standardized language for defining, querying, and manipulating data in relational database management systems. Its declarative statements specify desired data operations without prescribing how a database executes them.
SELECT statement : An SQL statement that retrieves rows and columns from one or more tables or other queryable sources. It expresses the central SQL operation: specifying which data to retrieve.
Relational model : A data model that represents information as relations, commonly displayed as tables of rows and columns. SQL's core structures and operations are grounded in this model.
Data definition language : The subset of a database language used to define or alter structures such as tables and schemas. SQL statements such as CREATE and ALTER define database structures.
NoSQL : A broad category of database systems that use data models other than the traditional relational model, or relax its conventions. NoSQL systems offer alternatives to the relational storage model SQL commonly addresses.
Edgar F. Codd : A British computer scientist whose 1970 paper introduced the relational model of data. Codd's model supplied the theoretical foundation that SQL systems adopted.
SQL query optimizer : A database component that chooses an execution plan for a query using estimates of cost and data distribution. It turns declarative SQL into an efficient physical execution strategy.
Database table : A database structure that organizes records into rows and attributes into columns. Tables are the primary structures SQL defines and manipulates.
Data manipulation language : The subset of a database language used to retrieve, insert, update, or delete data. SQL statements such as SELECT, INSERT, UPDATE, and DELETE manipulate records.
Relational database : A database that organizes data into relations and supports operations grounded in the relational model. SQL is most closely associated with managing this broader class of systems.
Donald D. Chamberlin : An American computer scientist who co-designed SEQUEL, the predecessor of SQL, at IBM. His work helped turn relational ideas into a practical query language.
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