This document is a general tutorial on the database sublanguage - SQL. It is not product oriented but rather uses standard SQL (SQL92). The tutorial doesn't cover all of SQL92; it concentrates on a subset of the standard that is both usable and commonly supported.
SQL (Structured Query Language) is a database sublanguage for querying and modifying relational databases. It was developed by IBM Research in the mid 70's and standardized by ANSI in 1986.
The Relational Model defines two root languages for accessing a relational database -- Relational Algebra and Relational Calculus. Relational Algebra is a low-level, operator-oriented language. Creating a query in Relational Algebra involves combining relational operators using algebraic notation. Relational Calculus is a high-level, declarative language. Creating a query in Relational Calculus involves describing what results are desired.
SQL is a version of Relational Calculus. The basic structure in SQL is the statement. Semicolons separate multiple SQL statements.
SQL (Structured Query Language) is a database sublanguage for querying and modifying relational databases. It was developed by IBM Research in the mid 70's and standardized by ANSI in 1986.
The Relational Model defines two root languages for accessing a relational database -- Relational Algebra and Relational Calculus. Relational Algebra is a low-level, operator-oriented language. Creating a query in Relational Algebra involves combining relational operators using algebraic notation. Relational Calculus is a high-level, declarative language. Creating a query in Relational Calculus involves describing what results are desired.
SQL is a version of Relational Calculus. The basic structure in SQL is the statement. Semicolons separate multiple SQL statements.
