Which of the following is NOT one of the common categories for SQL CHECK constraints used to limit acceptable values?

Introduction / Context:
CHECK constraints are declarative rules attached to a table that validate each row against logical conditions. Understanding common patterns helps design robust, self-enforcing schemas.

Given Data / Assumptions:

• We compare typical categories of CHECK logic.
• We look for the option that does not describe a common category.
• CHECK operates per-row and is evaluated at INSERT/UPDATE.

Concept / Approach:
Common CHECK uses include range checks, membership in a set, column-to-column comparisons within the same row, and simple pattern checks. While one can reference deterministic functions, loosely referring to “system date” as a general category is not standard; moreover, some systems restrict nondeterministic references in CHECK constraints to maintain consistency across statements.

Step-by-Step Solution:

Verification / Alternative check:
Vendor docs illustrate CHECK with expressions like col BETWEEN low AND high, col IN (...), col1 < col2, or col LIKE 'A%'; “system date” is a special-case function usage, not a category.

Why Other Options Are Wrong:
Range checks / lists / column comparisons / pattern checks: All are standard and portable uses of CHECK constraints.

Common Pitfalls:
Depending on nondeterministic functions (like current timestamp) in constraints can lead to nonportable behavior and unexpected validation results.

Final Answer:
System date (e.g., tying acceptance to the server's current date in general)