In SQL, what is Data Control Language DCL and what is its main purpose?

Introduction / Context:
Data Control Language, often abbreviated as DCL, is one of the important categories of SQL statements. While other categories such as DDL and DML focus on database structure and data manipulation, DCL is concerned with controlling who can do what in the database. Understanding DCL is fundamental for managing security and enforcing access policies in multi user environments.

Given Data / Assumptions:

• The question asks for the definition and purpose of Data Control Language DCL.
• We know that SQL is divided into sub languages like DDL, DML, DCL, TCL, and sometimes DQL.
• Common DCL statements include GRANT and REVOKE.
• The focus is on user access, permissions, and security.
• Other options describe different SQL categories such as DDL and DML.

Concept / Approach:
DCL statements are used by database administrators and sometimes advanced users to control access to database objects. The GRANT statement provides specific privileges to users or roles, such as permission to SELECT from a table or EXECUTE a stored procedure. The REVOKE statement removes previously granted permissions. Together, these statements manage which users can read, modify, or execute particular database resources, forming a key part of database security.

Step-by-Step Solution:
Step 1: Recall that DCL is distinct from DDL and DML, which manage structure and data respectively. Step 2: Identify typical DCL commands, namely GRANT and REVOKE. Step 3: Recognise that these commands specify which privileges users or roles have over database objects. Step 4: Compare this understanding with the answer options and choose the one that emphasises managing user access and privileges. Step 5: Confirm that this matches how DCL is described in SQL documentation and training materials.

Verification / Alternative check:
If you examine SQL reference guides for major databases such as Oracle or SQL Server, you will find a section on DCL that covers GRANT and REVOKE, describing them as commands used to control access rights. In contrast, DDL covers statements like CREATE and ALTER, and DML covers INSERT, UPDATE, and DELETE. This consistent categorisation confirms that DCL is about permissions and security.

Why Other Options Are Wrong:
Option A describes Data Definition Language DDL, which defines and modifies database objects. Option B describes Data Manipulation Language DML, which changes the data stored in tables. Option D refers to Transaction Control Language TCL, which manages transactions using COMMIT and ROLLBACK. Option E focuses on reading data, which is generally associated with SELECT and DQL, not specifically with DCL.

Common Pitfalls:
A frequent confusion is mixing up DCL and DDL because both types of statements may require high privileges. Another pitfall is assuming that SELECT permissions are part of DML because SELECT accesses data, when in fact the act of granting or revoking that permission is a DCL function. Remember that DCL is specifically about controlling who has access to perform operations, rather than about performing those operations themselves.

Final Answer:
Data Control Language DCL is a set of SQL statements used to manage user access, permissions, and security privileges in the database..