SQL (Structured Query Language)


SQL is a query language for interrogating, altering and managing relational databases. It is an ISO standard (ISO/IEC 9075). Notable Open Source DBMS packages that use SQL include MySQL, PostgreSQL and SQLite.

Data in an SQL database is stored in tables. A table is a two-dimensional structure with a fixed number of columns and a variable number of rows. Each column has a name and a type, and each row contains a value for each column. The combination of values in any row is unique within the table.

SQL queries are declarative in nature, meaning that they define the result that is needed but not the method by which it should be obtained. This has the effect of insulating client programs from some details of how the database is implemented, and transferring most of the burden of constructing efficient queries to the DBMS.


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