DDL vs. DML

Attribute	DDL	DML
Definition	Data Definition Language	Data Manipulation Language
Purpose	Used to define and manage database structure	Used to manipulate and retrieve data within the database
Operations	Create, alter, drop, truncate, rename	Select, insert, update, delete
Focus	Structure and organization of data	Manipulation and retrieval of data
Impact	Permanent changes to the database structure	Temporary changes to the data within the database
Examples	Create table, alter table, drop table	Select * from table, insert into table, update table set column=value

Introduction

Data Definition Language (DDL) and Data Manipulation Language (DML) are two essential components of Structured Query Language (SQL), which is widely used for managing and manipulating data in relational databases. While both DDL and DML are crucial for working with databases, they serve different purposes and have distinct attributes. In this article, we will explore the characteristics of DDL and DML, highlighting their differences and explaining their importance in the database management process.

DDL: Data Definition Language

DDL is a subset of SQL that focuses on defining and managing the structure of the database. It provides commands for creating, altering, and dropping database objects such as tables, views, indexes, and constraints. The primary goal of DDL is to establish the schema or blueprint of the database, ensuring data integrity and consistency. DDL commands are executed less frequently compared to DML, as they are typically used during the initial setup or when modifying the database structure.

DDL commands includeCREATE,ALTER, andDROP. TheCREATE command is used to create new database objects, such as tables or indexes. It specifies the object's name, attributes, and constraints. TheALTER command allows modifications to existing objects, such as adding or removing columns from a table. TheDROP command is used to delete an entire object from the database.

One of the key attributes of DDL is that it is an atomic operation. This means that DDL commands are executed as a single, indivisible unit. If any part of the command fails, the entire operation is rolled back, ensuring the database remains in a consistent state. Additionally, DDL commands are typically executed by database administrators or users with elevated privileges, as they have the authority to modify the database structure.

DML: Data Manipulation Language

DML, on the other hand, is concerned with manipulating the data stored within the database. It allows users to insert, retrieve, update, and delete data from the database tables. DML commands are executed more frequently compared to DDL, as they are used to perform day-to-day operations on the data.

DML commands includeSELECT,INSERT,UPDATE, andDELETE. TheSELECT command is used to retrieve data from one or more tables based on specified conditions. It allows users to filter, sort, and aggregate data to obtain meaningful results. TheINSERT command is used to add new rows of data into a table. TheUPDATE command allows users to modify existing data within a table. TheDELETE command is used to remove specific rows of data from a table.

Unlike DDL, DML commands are not atomic operations. They can be executed individually or as part of a larger transaction. Transactions allow multiple DML commands to be grouped together, ensuring that either all the changes are committed or none of them are. This helps maintain data integrity and consistency within the database.

Key Differences

While both DDL and DML are essential for managing databases, there are several key differences between them:

• DDL focuses on defining and managing the structure of the database, while DML is concerned with manipulating the data within the database.
• DDL commands are executed less frequently compared to DML commands.
• DDL commands are atomic operations, whereas DML commands can be executed individually or as part of a transaction.
• DDL commands are typically executed by database administrators or users with elevated privileges, while DML commands are executed by regular users.
• DDL commands includeCREATE,ALTER, andDROP, while DML commands includeSELECT,INSERT,UPDATE, andDELETE.

Conclusion

In summary, DDL and DML are two fundamental components of SQL that serve different purposes in managing and manipulating data within relational databases. DDL focuses on defining and managing the structure of the database, ensuring data integrity and consistency. DML, on the other hand, is concerned with manipulating the data stored within the database tables, allowing users to insert, retrieve, update, and delete data. Understanding the attributes and differences between DDL and DML is crucial for effectively working with databases and ensuring the proper management of data.