Language is a base for communication. To convey your message correctly to the audience, you need a mean to express your thoughts. Alike every language structured query language is a database management language for relational databases. It is a standardized programming language which is designed to manage structured data which shows the relationship between different variables of data. It came into existence in 1970's and was known as "SEQUEL." Later it was renamed as SQL. Initially it was only used by data administrators and data analysts. In 1979, it was launched for commercial purposes, and after that, it became the most widely used database language. In 1986, it was officially adopted by the American National Standards Institute (ANSI) and then by the International Organization for Standardization (ISO) in 1987. Initially, SQL was developed only to manage the data contained in a relational database, but currently, it is used as a tool of a developer. SQL is a broad programming language and consists different sub-languages. These five sub-languages and their uses are briefly discussed by SQL assignment help experts.
Different Sub-languages of SQL
SQL is divided in five principal sub languages that are discussed below:
1. Data Definition Language (DDL)
This sub-language is used to create tables and databases. It is also called as Data Description Language. It defines the properties of the particular table or a field. The specific commands allow to modify or destroy database variables. Presently, the database management industry includes DDL into any formal language describing data. The standard commands include English verbs to define the work. Some important statements are:
CREATE- It is usually used to create a database or its variables, such as index, views, function, and triggers.
ALTER- It is utilized to add a column in an existing table or to rename it. You can also change the data type of any column. You can also do some modification in the current table with this command.
DROP- The primary purpose of this command is to remove an object from the table in the database. If you want to delete all the rows from the table, then give drop command and the table structure will be removed from the database.
COMMENT- It is basically used to add comments to the data dictionary. The comments will help you understand the part of the statement in the program.
RENAME- This statement will rename a table or to rename an object already existing in the database.
TRUNCATE- It is used to delete all the records from the table as a whole. If you truncate the table, you can not undo it.
2. Data Manipulation Language (DML)
The main task of this sub-language is to manage data in a database. These commands are not auto-committed which means the modification done in the table is not permanent in the database, and it can be undone. As the name suggests, it manipulates the data and the objects in a table. It includes some common statements such as:
INSERT: It inserts or adds one or more data or records into a database table.
SELECT: It is utilized to recover rows from the table. It is the most used DML command in SQL.
UPDATE: This command updates the existing records into a table.
DELETE: This statement removes one or more records from the table.
3. Data Control Language (DCL)
The main purpose of this language is to see who can access the data stored in the database. Through this command, one can give or revoke the privilege applied to specific database objects. There are two essential commands in DCL.
GRANT- It merely allows the users to have access to the database.
REVOKE- It retracts the users privilege to access the database.
4. Transaction Control Language
It is used to manage transactions in the database. It is also used to commit and restore data. Some of the commands are as follows:
COMMIT: It is used to save any transaction into the database permanently.
ROLLBACK: It restores a database to a previously defined state if an error occurs.
SAVEPOINT: It is just like COMMIT command, but in this, the transaction is saved temporarily.
SET TRANSACTIONS: This statement is used to identify the point which can rollback if an error occurs in the transaction.
So, these are the primary sub-languages of SQL and their uses. Students often get confused in defining the commands; therefore we have highlighted the role of each statement so that you can have a clear understanding.
Summary: This article discusses the role of SQL sub-languages so that you can write a proper SQL assignment.