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SQL :
Structured Query Language (SQL) is a standard language for accessing and manipulating databases. The SQL language is sub-divided into several language elements, including
• Clauses which are in some cases optional, constituent components of statements and queries.
• Expressions which can produce either scalar values or tables consisting of columns and rows of data.
• Predicates which specify conditions that can be evaluated to SQL three-valued logic (3VL) Boolean truth values and which are used to limit the effects of statements and queries, or to change program flow.
• Queries which retrieve data based on specific criteria.
• Statements which may have a persistent effect on schemas and data, or which may control transactions, program flow, connections, sessions, or diagnostics.
SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar.
Different roles of SQL:
• SQL is an interactive query language. Users type SQL commands into an interactive SQL program to retrieve data and display it on the screen, providing a convenient, easy-to-use tool for ad hoc database queries.
• SQL is a database programming language. Programmers embed SQL commands into their application programs to access the data in a database. Both user written programs and database utility programs (such as report writers and data entry tools) use this technique for database access.
• SQL is a database administration language. The database administrator responsible for managing a minicomputer or mainframe database uses SQL to define the database structure and control access to the stored data.
• SQL is a client/server language. Personal computer programs use SQL to communicate over a network with database servers that store shared data. This client/server architecture has become very popular for enterprise-class applications.
• SQL is an Internet data access language. Internet web servers that interact with corporate data and Internet applications servers all use SQL as a standard language for accessing corporate databases.
• SQL is a distributed database language. Distributed database management systems use SQL to help distribute data across many connected computer systems. The DBMS software on each system uses SQL to communicate with the other systems, sending requests for data access.
• SQL is a database gateway language. In a computer network with a mix of different DBMS products, SQL is often used in a gateway that allows one brand of DBMS to communicate with another brand.
Structured Query Language (SQL) is a standard language for accessing and manipulating databases. The SQL language is sub-divided into several language elements, including
• Clauses which are in some cases optional, constituent components of statements and queries.
• Expressions which can produce either scalar values or tables consisting of columns and rows of data.
• Predicates which specify conditions that can be evaluated to SQL three-valued logic (3VL) Boolean truth values and which are used to limit the effects of statements and queries, or to change program flow.
• Queries which retrieve data based on specific criteria.
• Statements which may have a persistent effect on schemas and data, or which may control transactions, program flow, connections, sessions, or diagnostics.
SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar.
Different roles of SQL:
• SQL is an interactive query language. Users type SQL commands into an interactive SQL program to retrieve data and display it on the screen, providing a convenient, easy-to-use tool for ad hoc database queries.
• SQL is a database programming language. Programmers embed SQL commands into their application programs to access the data in a database. Both user written programs and database utility programs (such as report writers and data entry tools) use this technique for database access.
• SQL is a database administration language. The database administrator responsible for managing a minicomputer or mainframe database uses SQL to define the database structure and control access to the stored data.
• SQL is a client/server language. Personal computer programs use SQL to communicate over a network with database servers that store shared data. This client/server architecture has become very popular for enterprise-class applications.
• SQL is an Internet data access language. Internet web servers that interact with corporate data and Internet applications servers all use SQL as a standard language for accessing corporate databases.
• SQL is a distributed database language. Distributed database management systems use SQL to help distribute data across many connected computer systems. The DBMS software on each system uses SQL to communicate with the other systems, sending requests for data access.
• SQL is a database gateway language. In a computer network with a mix of different DBMS products, SQL is often used in a gateway that allows one brand of DBMS to communicate with another brand.
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