How do you manage permissions in SQL?

Managing permissions in SQL is done through GRANT and REVOKE statements, which control access to database objects like tables, views, or procedures. Permissions are assigned to users or roles (groups of permissions) to enforce security and limit data access. For example, you can grant a user permission to read a table but prevent them from modifying it. Most databases also support role-based access control (RBAC), allowing you to assign permissions to roles and then assign roles to users, simplifying management for teams.

First, define specific privileges using statements like GRANT SELECT ON employees TO user1;, which lets user1 read the employees table. Common privileges include SELECT, INSERT, UPDATE, DELETE, and EXECUTE (for stored procedures). To remove access, use REVOKE DELETE ON employees FROM user1;. Permissions can be granted at the column level (e.g., GRANT UPDATE (name) ON employees TO user1; in some databases) or restricted to specific operations. For roles, create a role (e.g., CREATE ROLE analyst;), grant it permissions (GRANT SELECT ON sales TO analyst;), then assign the role to users (GRANT analyst TO user2;).

Second, structure permissions hierarchically. For example, granting access to a schema (GRANT USAGE ON SCHEMA public TO user3;) or database (GRANT CONNECT ON DATABASE finance TO user4;) sets broader access boundaries. System-level permissions (e.g., CREATE TABLE) are managed separately. Always follow the principle of least privilege—grant only necessary permissions. Avoid using broad commands like GRANT ALL unless absolutely required, as this increases security risks.

Finally, audit permissions regularly. Use system tables (e.g., INFORMATION_SCHEMA.TABLE_PRIVILEGES in PostgreSQL) to review who has access. For example, querying SELECT * FROM information_schema.table_privileges WHERE grantee = 'user1'; shows permissions for user1. Revoke unused permissions (REVOKE INSERT ON orders FROM user5;) and update roles as team needs change. Different databases (MySQL, SQL Server, etc.) have slight syntax variations, but the core concepts remain consistent. Clear permission management ensures security while allowing developers and analysts to work efficiently.