SQL is a data based programming language. The name of the language is either pronounced as S-Q-L or it is simply termed as “sequel”. The abbreviation stand for Structured Query language. This language is mostly used to manage data in large quantities and helps to update the data into the server too. It is considered to be the most widely used language to manage relational database. SQL is the language which provides and easier method to view, read or write data into huge data banks. As data is considered to be the backbone of any company it is important to have a secured and closed programming language.
Donald D. Chamberlin and Raymond F. Boyce, who were working at IBM were the chief architects of SQL in the late 1970’s. It was initially called as SEQUEL( Structured English QUEry language). This was initially used only to retrieve and manipulate data from the IBM database. This later on was developed further to make a valuable product out of it.
Relational Database Management System was first developed in MIT. It was later given to US Navy, Central Intelligence Agency and similar such US organizations. In this way SQL became very popular in term so of usage and efficiency. Slowly IMB released test versions to public consumers and got how well the language is effective. This led to the commercial development of the product. Some of the known commercial products which were launched by IBM are System R, System/38, SQL/DS and DB2.
As stated before, SQL is used for data management and data manipulation. There are many other applications and usages of this particular language. To understand the effective working of SQL, one should understand the features that are provided in the language. Some of the essential language elements of SQL are
Queries – Queries are one of the most basic language elements which retrieve data from various tables the database has. These are denoted by a declarative SELECT. They mainly function as the data retrievers. They work let the user describe the data and leave a message to the database management system to perform the physical operations.
Data Manipulation – DML is the function which manipulates with the data. It is a subset of SQL which helps in adding, updating and deleting data.
INSERT – This adds data to the DBMS.
UPDATE – This modifies the existing data.
DELETE – This function will delete any data which is available in the DBMS.
MERGE – This will help you combine various tables in the DBMS. This is mostly known as the combine command for INSERT and UPDATE.
Transaction Controls - It is mostly a wrap DML operation. To make database transactions these elements are used. There are 2 major commands which are used in this, START TRANSACTION and SAVE TRANSACTION.
COMMIT permanent data changes will be made in the transaction will be made.
ROLLBACK it will change data only till the last changes were made. All the data before the previous change will be un-altered.
Data Definition – Data Definition Language helps to maintain tables and indexes. The most used commands used in this language are CREATE, ALTER, RENAME, DROP and TRUNCATE.
Data Types – The most common data types which are found in Database Management System are character strings, bit strings, numbers and date and time.
Data Control - Data Control Language ( DCL)is used to let users have control to update and manipulate data. There are two main statements which are used in this language.
GRANT – This statement will allow users to gain access to DBMS and manage the data.
REVOKE – This will eliminate the access of a user from the database.