DCL is a subset of Structured Query Language (SQL), which manages access to information stored in relational databases. It complements Data Definition Language, which creates and deletes database objects, and Data Manipulating Language, which retrieves, inserts, and modifies data within a database.

DCL, one of the simplest SQL commands, gives system administrators control over database permissions with GRANT, REVOKE and DENY statements. These three commands enable administrators to grant or revoke permissions in granular detail.

Definition

What is DCL (Data Control Language)?

DCL commands are part of the structured query language (SQL) that enables database administrators to manage access control by granting or revoking privileges. They provide granular control over data access, which is crucial for the security and integrity of stored information in a database.

GRANT Command: Grants user-specific permissions to perform certain operations on database objects such as tables and views. REVOKE Command: Revocates previously granted or denied permissions.

Joe is given permission to retrieve information from the employees’ table in a database. However, other users cannot view or access this table without authorization.

The GRANT command is one of the simplest among the three SQL commands, and it grants users a set of permissions that enable them to complete specific tasks.

REVOKE is a more complex command that cancels previously granted or denied permissions on a database object. To do this, the user must specify which database object had previously granted them access, then remove both granted permissions and denials from that object.

DCL commands in a multi-user system offer additional protection by extending XDB Server’s automatic record and table-level locking functions by acquiring explicit locks on specific database objects. Once connected to an established XDB Server or DB2 location, this becomes the current database location for all applications and users.

Purpose

The Data Control Language (DCL) is a subset of Structured Query Language (SQL), designed to control access to database objects like tables and views. DCL statements determine who has permission to view data stored in a database and perform certain actions on that data.

DCL commands enable database administrators to grant or revoke privileges and permissions to restrict access to a database. This control is essential for protecting sensitive data and preventing unauthorized users from changing the database.

GRANT is an essential DCL command that enables system administrators to grant permissions to specific users. The GRANT command consists of two parts: the OPTION clause, which specifies what rights are granted to a user, and the PERMISSION clause, which details which database permissions should be granted to that user.

When the GRANT command is executed, it grants the identified user privileges for INSERT, DELETE, SELECT, UPDATE, EXECUTE and ALTER operations. Conversely, REVOKE reverses any particular GRANT and DENY permissions assigned to a user, returning them to their default state.

DCL supports granting and revoking privileges for transactions in PostgreSQL and rollbacks of those transactions. A ROLLBACK statement effectively ends the current transaction and returns it to a savepoint in the database where all changes made during that transaction can be undone.

Example

DCL (Data Control Language) is an element of SQL (Structured Query Language). Its syntax resembles that of a computer programming language and serves to manage access to stored data.

Data manipulation language consisting of SQL commands for working with database objects like tables, views, functions, and procedures

The GRANT command in SQL allows a database administrator to grant users specific privileges or permissions on various database objects. Conversely, the REVOKE command allows one to revoke previously granted privileges or permissions.

Grant and revoke commands are commonly utilized for managing user permissions, rights, and other database system controls in a multi-user environment. Furthermore, these commands enforce database security within the environment by controlling access to certain areas.

The GRANT command allows the user to grant permissions on an object, such as a table, view, or procedure. Conversely, the REVOKE command can revoke previously granted privileges on either the same object or another one.

Types

Data control language (DCL) is a subset of Structured Query Language (SQL), which restricts access to database data. It helps protect that information by setting privileges for users within the database.

DCL provides two commands, GRANT and REVOKE, that manage a database system’s rights, permissions, and other controls. This is one of DCL’s most important capabilities as it helps prevent many issues caused by multiple users accessing the same Database.

GRANT Command: Database administrators often rely on this command to grant specific users permission to perform certain tasks within the database. It gives them access to specific database objects like tables or views.

REVOKE Command: Database administrators use this command to revoke user permissions on particular objects or commands that had previously been granted with a GRANT command. In essence, this means the user cannot perform certain operations such as INSERT or UPDATE any longer.

Additionally, database administrators have the authority to grant or revoke user privileges, thus avoiding potential issues due to the exposure of the database to multiple users. Moreover, it saves time as these rights are automatically assigned to users.

Commands

DCL is a subset of the Structured Query Language (SQL). It’s used to restrict access to database objects and the information stored within them by granting and revoking privileges to users or roles.

DCL commands such as GRANT, REVOKE, and DENY enable administrators to precisely set and remove database permissions.

GRANT command grants specific privileges or permissions to a user on database objects, such as tables, views, and procedures.

The REVOKE command disables a user’s access to certain database objects or functions, such as a query or insert.

The example below demonstrates how to utilize both GRANT and REVOKE commands.

DQL statements are part of SQL commands that permit the user to extract and organize data from a database, much like what projection operators do in relational algebra.

SELECT: This command enables the user to select data from a table and store it in a temporary table that the program can display or receive.

ALTER: This command allows you to modify the structure of a database or modify existing attributes.

UPDATE: This command allows you to modify data in a table.

DELETE: This command can be used to remove data from a table.

These are the most frequently used SQL commands. Other commands include COMMIT, DROP, and SAVEPOINT.

TCL vs. SQL

SQL (String Query Language) is an ANSI-standard programming language for creating and manipulating data in relational databases. It has been designed with portability, making it simple for people to communicate and share data from their devices.

However, some critics contend that SQL departs from the theoretical foundations of the relational model and its tuple calculus. For instance, a table in SQL is simply an array of rows; one row may appear multiple times, and the order of these rows can be altered through queries (e.g., using LIMIT clauses).

DCL (Data Control Language) is a sublanguage of SQL that contains commands for giving, revoking, and changing permissions on database objects. It helps enforce data security by blocking unauthorized access to information and enabling only authorized personnel to make modifications.

DDL and DML work together to manage and control user rights within a database. It offers an efficient method of restricting user access while protecting database security.

SQL injection attacks are the simplest of three SQL commands for controlling and granting database permissions. They give database administrators the power to grant, remove or set privileges as desired, ensuring data safety by restricting who can access data. Furthermore, this prevents inappropriate and potentially malicious techniques like SQL injection attacks from taking hold.

Permissions And Security

Data control language (DCL) is used to administrate access (permissions/security) to database content.  The main DCL commands are:

• Grant
• Revoke