Introduction to SQL

1 Introduction to SQL


The name SQL is pronounced as “ess-cue-ell” or ‘sequel’ is the abbreviation for structured query language.SQL is simple and powerful language used to create,access and mainipulate data and structure in the database.SQL is like plain English and easy to understand and to write.It has been accepted as an American standard by American National Standard Institute(ANSI) and is Federal Information Processing Standard(FIPS). .
SQL provides a small and concise set of commands.This helps us to save time and reduce amount of programming required to perform complex queries.SQL also helps us to modify a database application in a much easier way. Some common relational database management system that use SQL are: Oracle,Sybase,Microsoft SQL Server,Access etc.

What Can SQL do?
• SQL can execute queries against a database.
• SQL can retrieve data from a databse.
• SQL can insert records in a databse.
• SQL can update record in a database.
• SQL can delete records from a database.
• SQL can create new dadabases.
• SQL can create new tables in a database.
• SQL can create stored procedures in a database.
• SQL can create views in a database.
• SQL can set permissions on tables,procedures and views.

Characteristics of SQL
1. The following are the important characteristics of SQL.
2. SQL is extremely flexible
3. SQL uses a free form syntax that give the user the ability to structure SQL statements in a way best suited.
4. It is a free formatted languages i.e there is no need to start SQL statement in a particular column or to ne finished in a single line.
5. It has relatively few commands.
6. It is a non-procedural language.

ADVANTAGES OF SQL
1. The language while being simple and easy to learn can cope with complex situations
2. The results to be expected are well defined. As the language has a sound theoretical base, there is no ambiguity about the way a query will interpret the data and procedure the results.
3. SQL enables end users and systems personnel to deal with a number of database management systems where it is available. Increased acceptance and availability of SQL are also in it favour.
4. Applications written in SQL can be easily ported across systems. Such porting could be when the underlying DBMS (Database 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.
5. SQL as a language is independent of the way it is implemented internally. A query returns the same result regardless of whether optimizing has been done with indexes or not.
6. SQL is a unified language. The same language is used to define data structure,quering data, control access to data,insert,delete and modify occurrences of data & so on.
7. All programs written in SQL are portable thus they can be moved from one database to another with very little modification.
8. SQL enables its users to deal with a number of database management system where it is available.
9. It provides a greater degree of abstraction .The programmer has to specify what data is needed but need not specify, how to retrieve it.