Unit_2-2_Data_Management(SQL).pdf - O Structured Query Language In This Chapter 12.1 Introduction The Structured Query Language(SQL is a language that

Unit_2-2_Data_Management(SQL).pdf - O Structured Query...

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Structured Query Language STRUCTURED QUERY LANGUAGE 12.1 INTRODUCTION The Structured Query Language (SQL) is a language that enables you to create and operate on relational databases, which are sets of related information stored in tables. The database world is becoming increasingly integrated, and this has led to a clamor for a standard language that can be used to operate in many different kinds of computer environment. The SQL (Structured Query Language) has proved to be a standard language as it allows users to learn one set of commands and use it to create, retrieve, alter, and transfer information regard- less of whether they are working on a PC, a workstation, a mini, or a mainframe. There are numerous versions of SQL . The original version was developed at IBM’s San Jose Research Laboratory (now the Almanden Research Center ). This language, originally called Sequel , was implemented as part of the System R project in early 1970s. The Sequel language has evolved since then, and its name has changed to SQL . In 1986, the American National Standards Institute ( ANSI ) published an SQL standard that was updated again in 1992 ; latest ISO standard of SQL was released in 2008 and named as SQL:2008 . SQL has clearly established itself as the standard relational database language. In this chapter, we present a briefed survey of SQL . 12.2 PROCESSING CAPABILITIES OF SQL The SQL has proved to be a language that can be used by both casual users as well as skilled programmers. It offers a variety of processing capabilities, simpler ones of which may be used by the former and the more complex by the latter class of users. (12.1) SQL – Structured Query Language SQL is a simple query language used for accessing, handling and managing data in relational databases. N OTE Latest SQL standard as of now is SQL:2008 , released in 2008. In This Chapter 12.1 Introduction 12.2 Processing Capabilities of SQL 12.3 Data Definition Language 12.4 Data Manipulation Language 12.5 SQL Processing DHANPAT RAI & CO.
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The various processing capabilities of SQL are : 1. Data Definition Language ( DDL ). The SQL DDL provides commands for defining relation schemas, deleting relations, creating indexes, and modifying relation schemas. 2. Interactive Data Manipulation Language ( DML ). The SQL DML includes a query language based on both the relational algebra and the tuple relational calculus. It also includes commands to insert, delete, and modify tuples in the database. 3. Embedded Data Manipulation Language. The embedded form of SQL is designed for use within general-purpose programming languages such as PL/1, Cobol, Fortran, Pascal, and C. 4. View Definition . The SQL DDL also includes commands for defining views. 5. Authorization . The SQL DDL includes commands for specifying access rights to relations and views. 6. Integrity . The SQL provides (limited) forms of integrity checking. Future products and standards of SQL are likely to include enhanced features for integrity checking.
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