**Data Control Language (DCL)** is a subset of SQL used to **control access** to data stored in a relational database management system.   
DCL commands are primarily concerned with granting or revoking privileges on database objects such as tables, views, and schemas.

## DCL commands
The two main DCL commands are:

1. `GRANT`: This command is used to give specific privileges to users or roles;

2. `REVOKE`: This command is used to remove specific privileges from users or roles that have been previously granted.
## Privileges

## Implementation
To grant some privileges for an object in SQL for a particular user we can use the following statement: 
```sql
GRANT privileges
ON object
TO {user | role | PUBLIC};
```
There are 3 types of roles in DB to which you can grant some privileges:
- **user**: An individual database user;
- **role**: A database role, a named group of privileges that can be assigned to users (e.g. admin, developer, analyst);
- **PUBLIC**: A special keyword that grants the specified privileges to all users.

We can grant a role to a user using the following statement:
```sql
GRANT role TO user;
```
Finally, we can revoke previously granted privileges using the following statement:
```sql
REVOKE privileges
ON object
FROM {user | role | PUBLIC};
```





## Example
Here are some examples of how to use the `GRANT` command to assign different privileges on the bankaccounts and userlogs tables to different roles and users.
```sql
-- Create role
CREATE ROLE bank_manager;

-- Grant privileges to bank_manager role
GRANT SELECT, INSERT, UPDATE, DELETE ON BankAccounts TO bank_manager;
GRANT SELECT, INSERT ON UserLogs TO bank_manager;

-- Create users
CREATE USER john WITH PASSWORD 'password123';
CREATE USER jane WITH PASSWORD 'password456';

-- Assign roles to users
GRANT bank_manager TO john;
GRANT bank_manager TO jane;
```
Now we can revoke some of the granted privileges:
```sql
-- Revoke privileges from bank_manager role
REVOKE UPDATE, DELETE ON BankAccounts FROM bank_manager;
REVOKE INSERT ON UserLogs FROM bank_manager;

-- Revoke bank_manager role from john
REVOKE bank_manager FROM john;
```

What privilege allows a user to read data from a table?

Begin an exciting journey through SQL with Advanced Techniques in SQL. Learn about the important ACID properties that help keep data accurate in database transactions. Discover advanced ways to optimize your queries to improve database performance. Explore special SQL features like window functions, triggers, Data Control Language (DCL), and NoSQL databases. This will help you handle modern database management confidently and effectively.

Now we explore the basic principles of ACID (Atomicity, Consistency, Isolation, Durability) in database management. Learn how these principles ensure reliable transactions by guaranteeing complete operations, keeping data consistent, isolating concurrent transactions, and ensuring permanent data storage.

Explore how to enhance the efficiency of your SQL queries through index optimization. Delve into the significance of indexes in database performance, learning how to design, implement, and utilize them effectively. Discover strategies for choosing the appropriate indexes, understanding their impact on query execution plans, and optimizing query performance through index selection and utilization.

This section explores pivotal topics such as Triggers, Window Functions, and DCL (Data Control Language), offering comprehensive insights into their implementation and optimization strategies. Furthermore, it navigates the landscape of NoSQL DBMS, providing a thorough understanding of its architecture, advantages, and practical applications.

Advanced Techniques in SQL

Data Control Language

DCL commands

Privileges

Objects

Implementation

Example