EDUCBA

EDUCBA

MENUMENU
  • Free Tutorials
  • Free Courses
  • Certification Courses
  • 360+ Courses All in One Bundle
  • Login

Data Definition Language

By Priya PedamkarPriya Pedamkar

Home » Data Science » Data Science Tutorials » Database Management Tutorial » Data Definition Language

Data Definition Language

Introduction to Data Definition Language

Data Definition Language is a programming language through which data structures are defined. Acronymed as DDL, it can be considered as a standard that specifies commands through which data structures are defined.

There are four kinds of data languages:

Start Your Free Data Science Course

Hadoop, Data Science, Statistics & others

  • Data Definition Language (DDL): Code the data structures.
  • Data Manipulation Language (DML): Store and play with the data in those structures.
  • Data Control Language (DCL): Decide who can play with the structure as well as the data.
  • Data Query Language (DQL): Query the database for results and data mining.

Thus, in the simplest terms, DDL is a computer language used to code data structures.

Why Data Definition Language?

Data Definition Language dates back to the CODASYL database model. The schema of the database was written in a syntactical language. It was thorough in its description of the records, sets, fields, and the model as a whole. This was gradually adopted as a standard for declaring tables, columns, constraints, etc in Structured Query Language (SQL). Thus, over time, DDL became a subset of SQL.

How Data Definition Language Works?

DDL is a set of guidelines to which all the Structured Query Languages adhere to. As in the computer programming languages, we have the OOPS guidelines that all the programming languages adhere to, similarly, we have Data Definition Language standards that all the database languages adhere to – MySQL, Oracle, SQL Server, etc.

Data Definition Language deals with the structure of the database where the data is to be stored. It does not deal with the data itself. Thus, in any structured query language, a command that can modify the structure or the tables or relations of the database, is a DDL command. A command that modifies the data stored is a DML command. A command that modifies the authorization rules is a DCL command. A command that queries the database to fetch results is a DQL command.

Data Definition Language Commands

One thing needs to be thoroughly kept in mind – DDL deals with the structure of the database and not the data itself.

1. CREATE

So, the first command under DDL is the Create command. The Create command is used to create a new database or a new component in the database like tables, stored procedure, index, etc.

Let’s see all the commands one by one in action.

Note 1: The examples below use MySQL v8.0.16 CLI.
Note 2: Most of the structured query languages are case insensitive, which means the commands are the same whether in upper case or lower case.
CREATE DATABASE

The Create Database command creates a new database.

Syntax:

CREATE DATABASE <DatabaseName>

Example:

CREATE DATABASE ExampleDB;
CREATE TABLE

Now that we have a new database created, we need to create tables in our database.

Syntax:

CREATE TABLE <TableName> (
<Column1> <DataType>,
<Column2> <DataType>,
<Column3> <DataType>,
.
.
.
<ColumnN> <DataType>,
)

Example:

CREATE TABLE Employees (
Id INT,
Name VARCHAR(50),
Phone BIGINT,
IsContractor BIT
);

create

Our table is created. Now we can add data to it and query the results as and when needed.

2. ALTER

Now let’s look at the Alter commands in DDL. They are used to modify the tables to add, rename, edit or delete a column. Alter command can also rename the table itself.

Alter Table

Let’s see the various Alter DDL commands:

  • Add a column
  • The Alter Table command allows us to add a column to an existing table.

Syntax:

ALTER TABLE <TableName> ADD <ColumnName> <DataType>

Modify a column

The Alter Table command allows us to modify an existing column in an existing table. This is useful when modifying the type or the size of the column.

Syntax:

ALTER TABLE <TableName> MODIFY <ColumnName> <DataType>

An important thing to keep in mind is that we cannot rename a column with the modify sub-command. To rename, there is a separate sub-command.

Popular Course in this category
Sale
All in One Data Science Bundle (360+ Courses, 50+ projects)360+ Online Courses | 1500+ Hours | Verifiable Certificates | Lifetime Access
4.7 (3,220 ratings)
Course Price

View Course

Related Courses
SQL Training Program (7 Courses, 8+ Projects)PL SQL Training (4 Courses, 2+ Projects)Oracle Training (14 Courses, 8+ Projects)
Rename a table

The Alter Table command allows us to rename a table.

Syntax:

ALTER TABLE <TableName> RENAME TO <NewTableName>

Rename a column

The Alter Table command allows us to rename a column in an existing table.

Syntax:

ALTER TABLE <TableName> RENAME COLUMN <ColumnName> TO <NewColumnName>

Delete a column

The Alter Table command allows us to delete a column and its entire data from an existing table.

Syntax:

ALTER TABLE <TableName> DROP COLUMN <ColumnName>

Example:

Run the below lines of command in sequence to add a new column to the table, modify the type of the column, rename the column, drop the column and finally rename the table itself.

ALTER TABLE Employees ADD Department VARCHAR(20);
ALTER TABLE Employees MODIFY Department INT;
ALTER TABLE Employees RENAME COLUMN Department TO DepartmentId;
ALTER TABLE Employees DROP COLUMN DepartmentId;
ALTER TABLE Employees RENAME TO Employee;

alter command

3. DROP

The DROP commands are used to delete objects from the database or the schema. It can delete a table, view, stored procedure, index or even a database.

DROP TABLE

Drop Table command deletes the whole table along with all the data.

Syntax:

DROP TABLE <TableName>

Example:

DROP TABLE Employee;

DROP DATABASE

Drop Database command deletes the database and all the objects in it.

Syntax:

DROP DATABASE <DatabaseName>

Example:

DROP DATABASE ExampleDB;

drop command

Advantages

Below are some of the advantages explained.

  • The single largest advantage of Data Definition Language is uniformity.
  • A set of standards to which all Structured Query Languages conform.
  • Through DDL, the database schemas can be written in command forms and stored easily.
  • This also becomes easy to understand and write new command over time.
  • Thus, DDL, DML, DCL, and DQL bring uniformity at the very elementary level of all the structured query languages out there.

Conclusion

In this article, we have learned about the Data Definition Language, its concept, its purpose and a few examples in MySQL. It is recommended to understand the concept of DDL as it is a frequent test of knowledge in the Information Technology world.

Recommended Articles

This has been a guide to Data Definition Language. Here we discuss the basic concept, how it works along with advantages and disadvantages of data definition language. You may also have a look at the following articles to learn more –

  1.  Data Analysis Process
  2. Cassandra Data Types
  3. Best Data Visualization Tools
  4. What is R Programming Language?

All in One Data Science Bundle (360+ Courses, 50+ projects)

360+ Online Courses

1500+ Hours

Verifiable Certificates

Lifetime Access

Learn More

0 Shares
Share
Tweet
Share
Primary Sidebar
Database Management Tutorial
  • DataBase Management
    • Text Data Mining
    • Roles of Database Management System in Industry
    • SQL Server Database Management Tools
    • Database administrator skills
    • Database Management Systems Advantages
    • Database Testing Interview Questions
    • Data Administrator
    • Database Administrator
    • Database Management Software
    • DataStage
    • Types of Database Models
    • Types of Database
    • Hierarchical Database Model
    • Relational Database
    • Relational Database Advantages
    • Operational Database
    • What is RDBMS?
    • What is DB2?
    • Data Masking Tools
    • Database Security
    • Data Replication
    • Bitmap Indexing
    • Second Normal Form
    • Third Normal Form
    • Fourth Normal Form
    • Data Definition Language
    • Data Manipulation Language
    • Data Control Language
    • Transaction Control Language
    • Conceptual Data Model
    • Entity-Relationship Model
    • Relational Database Model
    • Sequential File Organization
    • Checkpoint in DBMS
    • Teradata Create Table
    • Centralized Database
    • Data Storage in Database
    • Thomas write Rule
    • DBA Interview Questions
    • What is JDBC?
    • jdbc hive
    • Apriori Algorithm
    • JDBC Architecture
    • JDBC Interview Questions
    • Wildcard Characters
    • Distributed Database System
    • Multidimensional Database
  • PL/SQL
    • What is PL/SQL?
    • Careers in PL/SQL
    • PLSQL procedure
    • PL/SQL Exception
    • PL/SQL LIKE
    • PL/SQL Raise Exception
    • PLSQL rowtype
    • PLSQL? bind variables
    • PL/SQL Record
    • PL/SQL WITH
    • PL/SQL bulk collect
    • PL/SQL Block Structure
    • PL/SQL else if
    • PL/SQL nvl2
    • PL/SQL Package
    • PL/SQL exists
    • PL/SQL instr
    • PL/SQL listagg
    • PL/ SQL Formatter
    • PLSQLlength
    • PL/SQL Commands
    • PL/SQL Data Types
    • CASE statement in PL/SQL
    • PL/SQL IF Statement
    • Loops in PL/SQL
    • PL/SQL Add Column
    • For Loop in PLSQL
    • PL/SQL Cursor Loop
    • PLSQL Array
    • Cursors in PL/SQL
    • PL/SQL FOR Loop Cursor
    • PL/SQL Queries
    • PL/SQL SELECT INTO
    • PL/SQL TO_CHAR
    • PL/SQL UNION
    • PL/SQL NOT EQUAL
    • PL/SQL varray
    • PL/SQL Concatenate
    • PL/SQL UPDATE
    • PL/SQL TRIM
    • PL/SQL GROUP BY
    • PL/SQL GOTO
    • PL/SQL Date Functions
    • PL/ SQL having
    • PL/SQL to_DATE
    • PL/SQL NVL
    • PLSQL format date
    • PLSQL mod
    • PLSQL round
    • PL/SQL Boolean
    • PL/SQL exit
    • PL/SQL DECODE
    • PL/SQL ROWNUM
    • PLSQL?pivot
    • PLSQL string functions
    • PL/SQL Block
    • PL/SQL Function
    • PL/SQL Unwrapper
    • PL/SQL Table
    • PL/SQL ALTER TABLE
    • PLSQL execute immediate
    • Triggers in PL/SQL
    • PL/SQL Collections
    • PL/SQL stored procedure
    • PL/SQL Anonymous Block
    • PLSQL Interview Questions
  • TSQL Basic
    • TSQL
    • What is T-SQL
    • T-SQL Commands
    • T-SQL String Functions
    • TSQL Interview Questions
  • MariaDB
    • MariaDB Versions
    • MariaDB?list users
    • MariaDB Commands
    • MariaDB Server
    • MariaDB? Data Types
    • MariaDB?boolean
    • MariaDB phpMyAdmin
    • MariaDB Mysqldump
    • MariaDB Java Connector
    • MariaDB insert
    • MariaDB UPDATE
    • MariaDB? rename column
    • MariaDB AUTO_INCREMENT
    • MariaDB Timezone
    • MariaDB GROUP_CONCAT
    • MariaDB wait_timeout
    • MariaDB MaxScale
    • MariaDB? with
    • MariaDB? create?table
    • MariaDB? SHOW TABLES
    • MariaDB alter table
    • MariaDB List Tables
    • MariaDB JSON Functions
    • MariaDB Foreign Key
    • MariaDB? trigger
    • MariaDB Grant All Privileges
    • MariaDB Select Database
    • MariaDB? create database
    • MariaDB Delete Database
    • MariaDB List Databases
    • MariaDB Functions
    • MariaDB? TIMESTAMP
    • MariaDB create user
    • MariaDB add user
    • MariaDB show users
    • MariaDB Delete User
    • MariaDB? change user password
    • MariaDB? change root password
    • MariaDB reset root password
    • MariaDB IF
    • MariaDB bind-address
    • MariaDB Transaction
    • MariaDB Cluster
    • MariaDB Logs
    • MariaDB Encryption
    • MariaDB? backup
    • MariaDB Replication
    • MariaDB max_allowed_packet
    • MariaDB? performance tuning
    • MariaDB export database
    • MariaDB? import SQL
  • SQLite
    • What is SQLite
    • SQLite Commands
    • SQLite Data Types
    • SQLite COUNT
    • SQLite Boolean
    • SQLite autoincrement
    • SQLite select
    • SQLite? Bulk Insert
    • SQLite? add column
    • SQLite? concat
    • SQLite BETWEEN
    • SQLite group by
    • SQLite CASE
    • SQLite group_concat
    • SQLite array
    • SQLite? enum
    • SQLite sum
    • SQLite create table
    • SQLite Alter Table
    • SQLite Create Database
    • SQLite Delete
    • SQLite connection string
    • SQLite Database
    • SQLite Describe Table
    • SQLite Show Tables
    • SQLite exit
    • SQLite create index
    • SQLite foreign key
    • SQLite Stored Procedures
    • SQLite Extension
  • DB2
    • DB2? current date
    • DB2 purescale
    • DB2 backup
    • DB2 restore
    • DB2 C Express
    • DB2 Version
    • DB2? Architecture
    • DB2? Data Types
    • DB2? load
    • DB2? order by
    • DB2 date
    • DB2 NVL
    • DB2? update
    • DB2 warehouse
    • DB2 grant
    • DB2 database
    • DB2 VARCHAR
    • DB2? INSERT
    • DB2 LISTAGG
    • DB2 LIKE
    • DB2 TRUNCATE TABLE
    • DB2 LIST TABLES
    • DB2 between
    • DB2? current timestamp
    • DB2? length
    • DB2? bind
    • DB2 limit rows
    • DB2? export
    • DB2 with
    • DB2 Create Table
    • DB2 case statement
    • DB2 CAST
    • DB2 Functions
    • DB2 Date Functions
    • DB2? row_number
    • DB2 trim
    • DB2? Translate
    • DB2 UNION
    • DB2 timestamp
    • DB2? TIMESTAMPDIFF
    • DB2? replace
    • DB2 merge
    • DB2 COALESCE
    • DB2 ISNULL
    • DB2? explain
    • DB2 Join
    • DB2 alter column
    • DB2 rename column
    • DB2? Describe Table
    • DB2? rename table
    • DB2 List Databases
    • DB2 LUW
    • DB2 Query
    • DB2 GROUP BY
    • DB2 TO_DATE
    • View Serializability in DBMS
    • MariaDB Join
    • MariaDB JSON
    • MariaDB? show databases
    • Dataset Normalization
    • MariaDB Max Connections
    • jdbc connection
    • MariaDB GUI
  • DBMS
    • Introduction To DBMS
    • DBMS ER Diagram
    • What is DBMS?
    • DBMS Canonical Cover
    • DBMS Log-Based Recovery
    • DBMS Multivalued Dependency
    • Netezza Database
    • DBMS Concepts
    • DBMS Constraints
    • DBMS_Scheduler
    • B+ Tree in DBMS
    • DBMS_LOB
    • dbms entity
    • DBMS Foreign Key
    • DBMS Users
    • DBMS_Metadata.get_ddl
    • Relational Algebra in DBMS
    • DBMS Components
    • DBMS Features
    • DBMS Models
    • DBMS Relational Model
    • Hashing in DBMS
    • DBMS network model
    • Relationship in DBMS
    • ER Model in DBMS
    • Data Models in DBMS
    • Static Hashing in DBMS
    • Advantages of DBMS
    • dbms_output.put_line
    • DBMS Data Dictionary
    • dbms_xplan.display_cursor
    • Normal Forms in DBMS
    • DBMS helps achieve
    • DBMS 3 tier Architecture
    • Relational Calculus in DBMS
    • Serializability in DBMS
    • File Organization in DBMS
    • DBMS Transaction Processing
    • States of Transaction in DBMS
    • Functional Dependency in DBMS
    • Generalization in DBMS
    • Data Independence in DBMS
    • Lock Based Protocols in DBMS
    • Deadlock in DBMS
    • Integrity Constraints in DBMS
    • Concurrency Control in DBMS
    • Validation Based Protocol in DBMS
    • DBMS Locks
    • Normalization in DBMS
    • Transaction Property in DBMS
    • Specialization in DBMS
    • Aggregation in DBMS
    • Types of DBMS

Related Courses

SQL Certification Course

PL/SQL Certification Course

Oracle Certification Course

Footer
About Us
  • Blog
  • Who is EDUCBA?
  • Sign Up
  • Live Classes
  • Corporate Training
  • Certificate from Top Institutions
  • Contact Us
  • Verifiable Certificate
  • Reviews
  • Terms and Conditions
  • Privacy Policy
  •  
Apps
  • iPhone & iPad
  • Android
Resources
  • Free Courses
  • Database Management
  • Machine Learning
  • All Tutorials
Certification Courses
  • All Courses
  • Data Science Course - All in One Bundle
  • Machine Learning Course
  • Hadoop Certification Training
  • Cloud Computing Training Course
  • R Programming Course
  • AWS Training Course
  • SAS Training Course

© 2022 - EDUCBA. ALL RIGHTS RESERVED. THE CERTIFICATION NAMES ARE THE TRADEMARKS OF THEIR RESPECTIVE OWNERS.

EDUCBA
Free Data Science Course

Hadoop, Data Science, Statistics & others

*Please provide your correct email id. Login details for this Free course will be emailed to you

By signing up, you agree to our Terms of Use and Privacy Policy.

EDUCBA
Free Data Science Course

Hadoop, Data Science, Statistics & others

*Please provide your correct email id. Login details for this Free course will be emailed to you

By signing up, you agree to our Terms of Use and Privacy Policy.

Let’s Get Started

By signing up, you agree to our Terms of Use and Privacy Policy.

Loading . . .
Quiz
Question:

Answer:

Quiz Result
Total QuestionsCorrect AnswersWrong AnswersPercentage

Explore 1000+ varieties of Mock tests View more

EDUCBA Login

Forgot Password?

By signing up, you agree to our Terms of Use and Privacy Policy.

This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in the cookie policy. By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to our Privacy Policy

EDUCBA

*Please provide your correct email id. Login details for this Free course will be emailed to you

By signing up, you agree to our Terms of Use and Privacy Policy.

Special Offer - All in One Data Science Bundle (360+ Courses, 50+ projects) Learn More