SQL Overview
SQL stands for Structured Query Language, used to store, retrieve, and manipulate data from a database. SQL is the standard language for RDBMS. SQL is one of the most commonly used query languages on databases.
Application :
1. SQL allow user to access the data from RDMS.
2. SQL allow user to store data.
3. SQL allow user to maipulate data.
4. SQL allow user to create or drop the databases and table.
5. SQL allow user to create function and views in a database.
This tutorial will give you a quick start to SQL. It covers most of the topics required for a basic understanding of SQL and to get a feel for how it works.
SQL Commands
Commands in SQL are classified into the following groups based on their data language. Standard SQL commands are CREATE, SELECT, INSERT, UPDATE, DELETE and DROP.
DDL - Data Definition Language
| Commands | Description |
|---|---|
| CREATE | The CREATE command is used to create or view tables in the database. |
| ALTER | The ALTER command is used to modify tables that already exist in the database. |
| DROP | The DROP command is used to delete tables in the database. |
DML - Data Manipulation Language
| Commands | Description |
|---|---|
| SELECT | The SELECT command is used to retrieve tuple or records from the database. |
| INSERT | The INSERT command is used to create tuple or records in the database. |
| UPDATE | The UPDATE command is used to modify existing records in the database. |
| DELETE | The DELETE command is used to delete records from the database. |
DCL - Data Control Language
| Commands | Description |
|---|---|
| GRANT | Gives a privilege to user. |
| REVOKE | Takes back privileges granted from user. |
RDBMS
RDBMS is concerned with relational database management system. Relational Database Management Systems (RDMS) such as MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their standard database language.
Difference between DBMS and RDBMS
| DBMS | RDBMS |
|---|---|
| Store data as file | Store data in a tabular form |
| Data stored in either a hierarchical form or a navigational form. | Data stored in the form of tables |
| Normalization is not present | Normalization is present |
| Does not apply any security | Defines the integrity constraint for the purpose of ACID |
| Does not support distributed database. | Support distributed database. |
| Examples are file systems, xml etc. | Example are mysql, postgre, sql server, oracle etc. |
Exercise:-
1. What is full form of RDBMS?
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2. Which of the following is not DML?
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