CHECK constraints in SQL: Judge the statement: "Common types of SQL CHECK constraints include range checks and limiting column values to allowed sets."

Introduction / Context: CHECK constraints are declarative integrity rules enforced by the DBMS to restrict allowed values in a column or tuple. They are a key tool for maintaining data quality at the database level rather than relying solely on application code.

Given Data / Assumptions:

• The statement references two common patterns: range checks and enumerated/domain checks.
• We assume a mainstream SQL DBMS supporting CHECK (e.g., PostgreSQL, SQL Server, Oracle, MySQL 8+ with CHECK enforced).

Concept / Approach: A CHECK constraint evaluates a Boolean expression per row. Typical constraints include ranges (e.g., salary between 0 and 1e7), set membership (e.g., status in ('NEW','SHIPPED','CLOSED')), simple relational expressions (start_date <= end_date), and pattern checks (LIKE, basic functions). These are classic, widely used patterns for enforcing domain integrity.

Step-by-Step Solution:

Verification / Alternative check: Inspect system catalogs to confirm constraints are stored and enforced; test with sample inserts to see violations blocked.

Why Other Options Are Wrong:

• Incorrect: Disagrees with standard practice.
• Deferrable only: Many CHECKs are NOT DEFERRABLE; deferrability is optional.
• Only ANSI, not vendors: Major vendors support CHECK; behavior nuances exist but concept holds.
• Only numeric: Strings, dates, and other types work too.

Common Pitfalls: Overusing triggers for validations that belong in CHECK; writing constraints that rely on subqueries (often disallowed in some DBMSs) instead of simpler per-row expressions.

Final Answer: Correct