What do you mean by SQL

Posted by Bhavesh Joshi On Monday, November 26, 2012 0 comments
Structured Query Language
SQL stands for structured query language. It is used to communicate with the database. Whenever any data is to be accessed from the database, we can do it through the SQL, and user can access the required data from the database, can manipulate data, can define the data in the database through SQL. SQL is a standard language for accessing databases.

SQL is supposed as structured query language for relational database management systems (RDBMS). SQL uses the combination of relational algebra and relational calculus constructs. It has many other capabilities besides querying the database. It includes the features of defining the structure of the data, for modifying data in the database and for specifying security constraints.

SQL has established as standard relational database language, and its original version was developed at IBM's San Jose Research Laboratory. It is also called SEQUEL and was implemented as part of the system R project. The purpose of this project was to validate the feasibility of relational model and to implement a DBMS based on this model. The results of this project are well documented in database literature. 

Additionally, to contributing to the concept of query compilation and optimization and concurrency control mechanisms, the most salient result of this project was the development of SQL. SQL is a nonprocedural language. Users describe in SQL what they want to do and the SQL language compiler automatically generates a procedure to navigate the database and performs the desired task.

Different parts of SQL

Different Parts of SQL 
  1. Data Definition Language: It provides the commands for defining relation schemas, deleting relations, creating indices and modifying relation schemas.

  2. Data Manipulation Language: It includes a query language based on both the relational algebra and the tuple relational calculus. It also provides commands to insert, delete, and modify tuples in the database. 

  3. View Definition: It includes commands for defining views. 

  4. Transaction Control: It includes commands for specifying the beginning and ending of transactions. 

  5. Integrity: The SQL DDL provides commands, for specifying integrity constraints, that the data stored in the database irriust satisfy. Updates that can violate integrity constraints are disallowed. 

  6. Authorization: The SQL DDL provides commands for specifying access rights to relations and views. 

  7. Embedded SQL and Dynamic SQL: Embedded and dynamic SQL define how SQL statements are embedded within programming languages such as C, C++, Java.


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