Answer :
The correct statement is c) One login can be linked to at most one database user in one database, and one database user can be linked to one login at most.
1. Login and Database User Relationship:
- A login is a credential that allows access to the database server instance.
- A database user is a security principal that is present in a specific database and can be mapped to a login.
2. One-to-One Relationship:
- In this context, one login can be linked to (or can correspond to) at most one database user within one database. This means each login can be associated with only one user in the database.
- Similarly, each database user is linked to one login only. There can't be multiple logins pointing to the same database user.
3. Example:
- Suppose we have a login named 'AdminLogin'. If 'AdminLogin' is linked to a user named 'AdminUser' in database 'DB1', this is the only link allowed. We cannot have 'AdminLogin' linked to another user in 'DB1' or have 'AdminUser' linked to another login.
4. Why This Matters:
- Ensuring a one-to-one relationship between logins and users adds a layer of security and simplifies database management. This way, permissions and access can be distinctly controlled.
Final answer:
The correct relationship between a login and database users in an instance is one-to-one, aligning with a baseball player having one unique jersey number.
Explanation:
The correct statement regarding the relationship between logins and database users in a database instance is that one login can be linked to at most one database user in one database, and one database user can be linked to one login at most. This relationship is best described as a one-to-one relationship, similar to a baseball player having a unique jersey number. In database terms, a login provides authentication, while a database user provides access to a specific database within an instance, under the context of the login.
The incorrect statements suggest either a one-to-many or many-to-many relationship, which would imply that a single login could be linked to multiple users in the same database or that a single user could be linked to multiple logins, neither of which is correct according to standard security practices in database management systems.
