25-08-2017, 09:32 PM
structured query language
INTRODUCTION TO SQL
SQL (structured query language) is a database computer language designed for the retrieval and management of data in relational database systems (RDBMS), database scheme creation and modification, and database object access control management.
FEATURES OF SQL
SQL is both an easy –to-understand language and a comprehensive tool for managing data.
High-level .English-like structure
Interactive, ad hoc queries
Programmatic database access
Multiple views of data
Complete database language
Dynamic data definition
Client/server architecture
TYPES OF SQL COMMANDS
SQL is used to control all of the functions that a DBMS provides for its users, including:
Data definition, SQL lets a user define the structure and organization of the stored data and relationship among the stored data items. Data retrieval, SQL allows a user or an application program to retrieve stored data from the database and use it. Data manipulation, SQL allows a user or an application program to update the database by adding new data, removing old data, and modifying previously stored data.
Access control, SQL can be used to restrict a user’s ability to retrieve, add, and modify data, protecting stored data against unauthorized access. Data sharing, SQL is used to coordinate data sharing by concurrent users, ensuring that they do not interface with one another.
Data integrity, SQL defines integrity constraints in the database, protecting it from corruption due to inconsistent updates or system failures.