Valid constraints in MySQL?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of SQL & Databases conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
MySQL supports a complete set of integrity constraints:
PRIMARY KEY: Uniquely identifies each row (impliesNOT NULLandUNIQUE).FOREIGN KEY: Enforces referential integrity matching a primary key in another table.UNIQUE: Guarantees all values in a column are distinct.NOT NULL: ProhibitsNULLvalues.CHECK(MySQL 8.0+): Validates that values satisfy a boolean expression (CHECK (age >= 18)).DEFAULT: Assigns a fallback value if omitted during insert.AUTO_INCREMENT: Auto-generates sequential integer identifiers.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.