In SQL, external tables allow you to access data stored outside the database using a structured query language. However, there may be instances when you need to revoke privileges for external tables to control data access and ensure data security. In this blog post, we will explore how to revoke external table privileges in SQL.

Syntax for Revoking Privileges

The syntax for revoking privileges on an external table varies depending on the database management system (DBMS) you are using. However, the general syntax follows similar patterns. Here is an example of how to revoke privileges on an external table:

REVOKE privileges ON external_table_name FROM user_name [CASCADE];

Let’s break down the syntax:

• REVOKE is the SQL keyword used to revoke privileges.
• privileges specify the specific privileges to be revoked, such as SELECT, INSERT, UPDATE, or DELETE.
• external_table_name refers to the name of the external table from which you want to revoke privileges.
• user_name represents the user or role from which the privileges will be revoked.
• CASCADE is an optional keyword that determines whether the revocation should cascade to dependent objects.

Example Usage

Suppose you have an external table named sales_data and you want to revoke the SELECT and INSERT privileges from the user sales_user. Here is an example query using the Oracle syntax:

REVOKE SELECT, INSERT ON sales_data FROM sales_user;

If you want to revoke the privileges for multiple users or roles, you can provide a comma-separated list of user names or roles.

REVOKE SELECT, INSERT ON sales_data FROM username1, username2;

By default, the revocation does not cascade to dependent objects. However, if you want the revocation to cascade and revoke privileges from dependent objects, you can include the CASCADE keyword.

REVOKE SELECT, INSERT ON sales_data FROM sales_user CASCADE;

Conclusion

Revoking external table privileges is an essential aspect of data security in SQL. By understanding the syntax and usage of the REVOKE statement, you can easily revoke privileges from external tables. Be sure to use this capability judiciously and only revoke privileges as required for your specific use case.

#SQL #DataSecurity