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What are SQL and RDBMS? - Computer awareness

What are SQL and RDBMS? Computer awareness

SQL (Structured Query Language) was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce in the early 1970s. This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasi-relational database management system. SQL (Structured Query Language) is a non-procedural language. SQL is used for access and manipulate data in databases. SQL is an ANSI (American National Standards Institute) standard language.

What Is SQL

SQL stands for Structured Query Language, which is a computer language for storing, manipulating, and retrieving data stored in a relational database. It is a language for Relational Database System. All the Relational Database Management Systems (RDMS) like MySQL, MS Access, Oracle, and SQL Server use SQL as their standard database language. Also, they are using different dialects, such as - 
  • MS SOL Server using T-SQL,
  • Oracle using PL/SQL,
  • MS Access version of SQL is called JET SQL (native format) etc.

SQL Sub Language

SQL is mainly divided into four sub language
  • Data Definition Language(DDL)
  • Data Manipulation Language(DML)
  • Transaction Control Language(DCL)
  • Data Control Language(DCL)

Only for remember

  1.  You can remember all these commands like below: DDI Commands "dr. cat" d-Drop, r-Renamc, e-Create, a-Alter, L-Truncate. 
  2. DML commands "sudi". s-Select, u-Update, d-Delete, i-Insert

Why need of SQL

SQL is so popular for the following advantages- 
  • To create new databases, tables. 
  • To insert any records in the database 
  • To delete records from the database 
  • To update records in the database 
  • To retrieve data from the database

Features of SQL 

  1. SQL is not a case sensitive language. 
  2. Every command in SQL should end with a semicolon(;)
  3. SQL can also be called a sequel (SEQUEL). 
  4. It is an ANSI (American National Standards Institute) standard language.

Limitation of SQL

  1. SQL does not support conditional and looping statements. 
  2. When the user performs any wrong transaction, SQL always gives system defined error message. 
  3. It cannot support to execute more than one statement at a time, so it increases the network traffic.
  4. SQL does not support the code re-usability;, it means you need to write insert, delete, update, select command each and every time. 
  5. SQL does not support procedure language features such as code reusability and molecularity and some other features of oops.
To Overcome all these above limitations we use PL/SQL

What is RDBMS?

RDBMS stands for Relational Database Management System. All modern RDBM database management systems like SOL, MS SOL Server, Oracle, MySQL, IBM DB2, and Microsoft Access are based on RDBMS. RDBMS was developed by a Jermen scientice Mr. E.F codd in 1970 this model was developed on the basis of a mathematical concept called relational algebra.

Relations are classified into three types, they are;
1. one to one Relationship 
In the relationship, one object has the only relation with another object.
2. One too many or many to one relationship
in the relationship one subject has a relation with many other objects.
3. Many-many Relationship
In this relationship, many objects have a relationship with many other objects.

Properties of RDBMS

  • Data should be stored in the form of table.
  • A table can be defined as a collection of rows and columns.
  • The horizontal lines are known as rows or tuples or records.
  • The vertical lines are known as a column or filed attributes.
  • The intersection of the row and column is known as the cell.
  • A cell is a place where you can store your data.
  • The other name of the table is called as entry or class or object.

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