SQL

SQL uses a combination of relational-algebra and relational-calculus constructs. The SQL language has several parts:

• Data-Definition Language (DDL) : The SQL DDL provides commands for defining relation schemas, deleting relations, and modifying relation schemas.
• Interactive Data-Manipulation Language (DML) : The SQL DML includes a query language based on both the relational algebra and the tuple relational calculus. It includes also commands to insert tuples into, delete tuples from, and modify tuples in the database.
• View Definition : The SQL DDL includes commands for defining views.
• Transaction Control : SQL includes commands for specifying the beginning and ending of transactions.
• Embedded SQL and Dynamic SQL : Embedded and dynamic SQL define how SQL statements can be embedded within general-purpose programming languages, such as C, C++, Java, PL/I, Cobol, Pascal, and Fortran.
• Integrity : The SQL DDL includes commands for specifying integrity constraints that the data stored in the database must satisfy. Updates that violate integrity constraints are disallowed.
• Authorization : The SQL DDL includes commands for specifying access rights to relations and views.