What type of isolation level should be used for a user table if each user has the right to modify only their records, and an administrator can modify any data?

For a user table where each user can only modify their own records, and an administrator can access any data, it is recommended to use the Read Committed or Repeatable Read isolation level in combination with access control at the application level.

Explanation:

• The isolation level manages the visibility of changes between transactions but does not provide access rights segregation.
• Read Committed prevents reading uncommitted data, which is usually sufficient for such scenarios.
• Access control is implemented through application logic or database security policies.

If a stricter isolation is needed to prevent phantom reads, Repeatable Read can be used, but it may reduce performance.

Important: The isolation level does not replace the authorization mechanism but complements it, ensuring data correctness during concurrent access.