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MySQL Data Types


MySQL supports a number of data types in several categories:
1. String (character and byte) types, and spatial types.
2. Date and time types
3. Numeric types

The following are the String Datatypes in MySQL:

String Data Types


The following are the Numeric Datatypes in MySQL:

Numeric Data Types


The following are the Date/Time Datatypes in MySQL:


What are the difference between DDL, DML and DCL commands?


SQL commands are instructions used to communicate with the database to perform specific task that work with data. SQL commands can be used not only for searching the database but also to perform various other functions like, for example, you can create tables, add data to tables, or modify data, drop the table, set permissions for users. SQL commands are grouped into four major categories depending on their functionality:

DDL : 

Data Definition Language (DDL) statements are used to define the database structure or schema. Some examples:

  • CREATE – to create objects in the database
  • ALTER – alters the structure of the database
  • DROP – delete objects from the database
  • TRUNCATE – remove all records from a table, including all spaces allocated for the records are removed
  • COMMENT – add comments to the data dictionary
  • RENAME – rename an object


Data Manipulation Language (DML) statements are used for managing data within schema objects. Some examples:

  • SELECT – retrieve data from the a database
  • INSERT – insert data into a table
  • UPDATE – updates existing data within a table
  • DELETE – deletes all records from a table, the space for the records remain
  • MERGE – UPSERT operation (insert or update)
  • CALL – call a PL/SQL or Java subprogram
  • EXPLAIN PLAN – explain access path to data
  • LOCK TABLE – control concurrency


Data Control Language (DCL) statements. Some examples:

  • GRANT – gives user’s access privileges to database
  • REVOKE – withdraw access privileges given with the GRANT command


Transaction Control (TCL) statements are used to manage the changes made by DML statements. It allows statements to be grouped together into logical transactions.

  • COMMIT – save work done
  • SAVEPOINT – identify a point in a transaction to which you can later roll back
  • ROLLBACK – restore database to original since the last COMMIT
  • SET TRANSACTION – Change transaction options like isolation level and what rollback segment to use

MySQL Introduction

What is database?

A database is a separate application that stores a collection of data. Each database has one or more distinct APIs for creating, accessing, managing, searching and replicating the data it holds.

Other kinds of data stores can be used, such as files on the file system or large hash tables in memory but data fetching and writing would not be so fast and easy with those types of systems.

So nowadays, we use relational database management systems (RDBMS) to store and manage huge volume of data. This is called relational database because all the data is stored into different tables and relations are established using primary keys or other keys known as foreign keys.

A Relational DataBase Management System (RDBMS) is a software that:

Enables you to implement a database with tables, columns and indexes.Guarantees the Referential Integrity between rows of various tables.Updates the indexes automatically.Interprets an SQL query and combines information from various tables.

RDBMS Terminology:

Before we proceed to explain MySQL database system, let’s revise few definitions related to database.
Database: A database is a collection of tables, with related data.

Table: A table is a matrix with data. A table in a database looks like a simple spreadsheet.

Column: One column (data element) contains data of one and the same kind, for example the column postcode.

Row: A row (= tuple, entry or record) is a group of related data, for example the data of one subscription.

Redundancy: Storing data twice, redundantly to make the system faster.

Primary Key: A primary key is unique. A key value can not occur twice in one table. With a key, you can find at most one row.

Foreign Key: A foreign key is the linking pin between two tables.

Compound Key: A compound key (composite key) is a key that consists of multiple columns, because one column is not sufficiently unique.

Index: An index in a database resembles an index at the back of a book

Referential Integrity: Referential Integrity makes sure that a foreign key value always points to an existing row.

What is MySQL?

MySQL is a open source, fast reliable and flexible relational database management system which are used with Php.

  • MySQL is a database system which is used for the developing web based software application.
  • This is used for both small and large applications.
  • It is relational database management system (RDBMS).
  •  MYSQL supports standard SQL.


  • MySQL server design is multi-layered with independent modules.
  • MySQL is fully multithreaded by using kernel threads.
  • It can use multiple CPUs if they are available.
  • It provides the transaction and non-transactional storage engine.
  • It has very fast thread -based memory allocation system.
  • It supports in-memory heap table.
  • It handles large databases.
  •  MySQL server works in client/server or embedded systems.
  •  It works on many different platforms.

Who uses MySQL?

  • Most popular websites: Facebook, Wikipedia, You Tube, Flickr etc.
  • Content Management System (CMS) like WordPress, Drupal, Joomla, phpBB.


MySQL Tutorial

SQL is a standard language for accessing databases.Our SQL tutorial will teach you how to use SQL to access and manipulate data in: MySQL, SQL Server, Access, Oracle, Sybase, DB2, and other database systems.

MySQL is the most popular Open Source Relational SQL database management system.

MySQL is one of the best RDBMS being used for developing web-based software applications.

This tutorial will give you quick start with MySQL and make you comfortable with MySQL programming.

What is the difference between waterfall and agile model

Difference between waterfall and agile model:

agile vs waterfall model

Waterfall- Deadlines are fixed of the project delivery.
Agile- Fast  and flexibility of the dead-line