What are DCL Commands in SQL?

What are DCL Commands in SQL?

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Vikram
Vikram Singh
Assistant Manager - Content
Updated on Sep 21, 2023 11:18 IST

SQL, or Structured Query Language, is a database language that allows you to create a database and perform various operations. This is done using various types of SQL commands, such as DDL, DQL, DML, TCL, and DCL. But, this article will mainly focus on DCL commands in SQL.

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Before we dive deeper into the article (DCL commands in SQL), let’s quickly go over the list of topics listed under the table of contents (TOC) that we will cover in this article. Here’s the table of contents:

Table of Contents (TOC)

What are DCL Commands in SQL

DCL Commands Definition: DCL or Data Control Language commands in SQL allow you to manage access control by either granting privileges to the users in a database or revoking their privileges.

With the help of DCL commands, you can easily define the level of access and permissions that users have on the database and its objects, such as tables, views, procedures, etc. In layman’s terms, Data Control Language commands in SQL allow database administrators to control who has access to the data in a database and what actions they can perform on that data.

You can also explore: All About DML Commands in SQL

You can also explore: What is the Difference Between SQL and MySQL?

Types of DCL Commands in SQL 

There are mainly two types of DCL commands in SQL that helps data administrator a lot in managing access control. These two types of Data Control Language commands are:

  • GRANT
  • REVOKE

Let’s explore the GRANT command in detail in the next section.

GRANT Command

GRANT Command Definition: The GRANT command allows the database administrator to grant specific privileges or permissions to a user on a database object, such as tables, views, procedures, etc. 

In layman’s terms, the GRANT command allows a user to access and perform specific actions on the database or its objects. You should also remember that the GRANT command is mainly used by database administrators in order to ensure the security and integrity of the data in the database. In order to better understand the working of the GRANT command, let’s go through an example.

GRANT Command Example:

Consider a database with a table named “employees.” If you want to allow a user named “Atul” to only SELECT (read) data from the “employees” table, you can use the following GRANT command:

 
GRANT SELECT ON employees TO Atul;
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This command will allow the user “Atul” to run SELECT queries on the “employees” table. But Atul won’t be able to make any changes, such as inserting, updating, or removing the data in the “employees” table.

REVOKE Command

REVOKE Command: The REVOKE command allows the database administrator to revoke previously granted privileges or permissions to a user on a database object, such as tables, views, procedures, etc. 

In layman’s terms, the REVOKE command restricts a user from accessing and performing specific actions on the database or its objects. You should remember that the REVOKE command is also mainly used by database administrators in order to ensure the security and integrity of the data in the database. In order to better understand the working of the REVOKE command, let’s go through an example.

You can also explore: 100+ SQL Interview Questions and Answers

REVOKE Command Example:

Let’s consider the above example that we discussed in the GRANT command. In that, we have granted access to Atul to SELECT (read) data from the “employees” table. Now, due to certain reasons, you want to revoke those permissions. Hence, you can use the following REVOKE command to remove that privilege:

 
REVOKE SELECT ON employees FROM Atul;
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This would revoke user “Atul”‘s ability to run SELECT queries on the “employees” table.

Advantages of DCL Commands 

There are various advantages to using DCL commands. Let’s explore some of the most common and popular advantages of DCL commands, such as:

  • Security: DCL commands allow database administrators to control who has access to the data in a database and what actions they can perform on that data. Thus, ensuring the security and integrity of the data stored in the database.
  • Granular control: DCL commands allow administrators to grant and revoke specific privileges and permissions, Thus giving differing levels of access (granular control) to a particular user.
  • Flexibility: The ability to grant and revoke privileges as per the requirements provides flexibility to database administrators in order to manage access to the database.

Must Check: Free Database and SQL Online Course and Certificates 

Disadvantages of DCL Commands 

Along with the advantages of using DCL commands, there are some drawbacks also. Some of the most common disadvantages of using data control language commands are:

  • Complexity: If there is a large number of users and the database is complex, then granting and revoking privileges can be complex and time-consuming.
  • Risk of human error: Human administrators execute DCL commands and can make mistakes in granting or revoking privileges. Thus, giving unauthorized access to data or imposing unintended restrictions on access.
  • Lack of audit trail: There may be no built-in mechanism to track changes to privileges and permissions over time. Thus, it is extremely difficult to determine who has access to the data and when that access was granted or revoked.

You can also explore: ACID Properties in SQL

Conclusion

In this article, we have discussed what data control language commands are. We have also explored its types with examples, advantages, and disadvantages of using these commands. If you have any queries related to the topic, feel free to send your query to us in the form of a comment. We will be happy to help.

Happy Learning!!

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FAQs

What is DCL in SQL?

DCL stands for Data Control Language. It's a component of SQL (Structured Query Language) that is used to implement security on database objects. DCL includes two commands, GRANT and REVOKE, which respectively allow permissions to be added or removed from database users.

What does the GRANT command do in SQL?

The GRANT command is used in SQL to give users authorization to perform various operations on the database. This might include permissions to SELECT, INSERT, UPDATE, DELETE, or other actions on a database object.

What does the REVOKE command do in SQL?

The REVOKE command is used in SQL to remove or reduce the permissions given to the database users. This command can undo the permissions set by the GRANT command.

Can the REVOKE command undo all permissions set by the GRANT command?

Yes, the REVOKE command can be used to undo all permissions set by the GRANT command. However, it's also possible to revoke only specific permissions while leaving others in place.

About the Author
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Vikram Singh
Assistant Manager - Content

Vikram has a Postgraduate degree in Applied Mathematics, with a keen interest in Data Science and Machine Learning. He has experience of 2+ years in content creation in Mathematics, Statistics, Data Science, and Mac... Read Full Bio