SQL, a Structured Query Language is now available with most RDBMS (Relational Database Management System) products as the database language. Which can be used both by end-users and system programmers.
Originally, SQL was called SEQUEL( for Structured English QUEry Language).
SQL is now standard language for commercial relational DBMS.
First reason, a query in relational algebra is written as a sequence of operations that, after execution, produce the required result. Hence, the user must specify how –that is, in what order – to execute the query operations.
On the other hand, the SQL provides a high-level declarative language interface, so the user only specifies what the result is to be, leaving the actual optimization and decision on how to execute the query to the DBMS.
Characteristics of SQL
User Friendly. The SQL syntax is more user-friendly than other formal languages.
Comprehensive database language. SQL is a comprehensive database language (DDL, DML & DCL); it has statements for data definition, query, and update. Also have a facility for defining views on the database, for specifying security and authorization, for defining integrity constraints, and for specifying transaction controls.
Easy to learn. The language while being simple and easy to learn can cope with complex situations.
SQL Applications can be easily ported across other systems. Such porting could be required when the underlying DBMS (Data Base Management System) needs to be upgraded because of change in transaction volumes or when a system developed in one environment is to be used on another DBMS.
The results to be expected are well defined.
Allow end-users and systems personnel to deal with a number of database management systems where it is available.
Independent Implementation : As a language its implementation is independent. A query return the same result regardless of whether optimizing has been done with indexes or not.
Embedded DML. It also has a rules for embedding SQL statements into a general-purpose programming language such as Fortran, Cobol, C and Pascal.