You want to ensure a discount column in a sales table is either NULL or between 0 and 50 inclusive. Which CHECK constraint correctly enforces this?

hard📝 Application Q8 of 15

SQL - Table Constraints

You want to ensure a discount column in a sales table is either NULL or between 0 and 50 inclusive. Which CHECK constraint correctly enforces this?

ACHECK (discount IS NOT NULL AND discount BETWEEN 0 AND 50)

BCHECK (discount >= 0 AND discount <= 50)

CCHECK (discount IS NULL OR (discount >= 0 AND discount <= 50))

DCHECK (discount > 0 AND discount < 50)

Step-by-Step Solution

Solution:

Step 1: Understand the requirement for discount
Discount can be NULL or a value from 0 to 50 inclusive.
Step 2: Analyze each CHECK condition
CHECK (discount IS NULL OR (discount >= 0 AND discount <= 50)) allows NULL or values between 0 and 50 inclusive, matching the requirement.
Final Answer:
CHECK (discount IS NULL OR (discount >= 0 AND discount <= 50)) -> Option C
Quick Check:
Use OR to allow NULL or valid range [OK]

Quick Trick: Use OR with IS NULL to allow nullable ranges [OK]

Common Mistakes:

MISTAKES

Forgetting to allow NULL values
Using strict > and < excluding boundaries
Requiring discount to be NOT NULL

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More SQL Quizzes

You want to ensure a discount column in a sales table is either NULL or between 0 and 50 inclusive. Which CHECK constraint correctly enforces this?

Step 1: Understand the requirement for discount

Step 2: Analyze each CHECK condition

Final Answer:

Quick Check:

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