A table has id INT PRIMARY KEY and score INT CHECK (score BETWEEN 0 AND 100). You want to add a constraint to ensure score is not NULL. What is the best way?

hard📝 Application Q9 of 15

SQL - Table Constraints

A table has id INT PRIMARY KEY and score INT CHECK (score BETWEEN 0 AND 100). You want to add a constraint to ensure score is not NULL. What is the best way?

AAdd CHECK (score IS NOT NULL) constraint

BAdd NOT NULL constraint to score column

CAdd UNIQUE constraint on score

DAdd DEFAULT 0 to score column

Step-by-Step Solution

Solution:

Step 1: Understand NOT NULL vs CHECK for NULL prevention
NOT NULL explicitly forbids NULL values; CHECK can test conditions but NOT NULL is clearer and standard.
Step 2: Evaluate options
Adding NOT NULL is best practice; CHECK (score IS NOT NULL) is redundant; UNIQUE unrelated; DEFAULT sets value but doesn't forbid NULL.
Final Answer:
Add NOT NULL constraint to score column -> Option B
Quick Check:
NOT NULL forbids NULL values best [OK]

Quick Trick: Use NOT NULL to forbid NULL values, not CHECK [OK]

Common Mistakes:

MISTAKES

Using CHECK to forbid NULL instead of NOT NULL
Confusing UNIQUE with NULL prevention
Assuming DEFAULT forbids NULL

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More SQL Quizzes

A table has id INT PRIMARY KEY and score INT CHECK (score BETWEEN 0 AND 100). You want to add a constraint to ensure score is not NULL. What is the best way?

Step 1: Understand NOT NULL vs CHECK for NULL prevention

Step 2: Evaluate options

Final Answer:

Quick Check:

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