Which change will prevent negative ages to be inserted into the people table?

Question

Options

• ADELIMITER //
• BALTER TABLE people ADD COLUMN valid_age=ABS(check_age) GENERATED ALWAYS;
• CDELIMITER //
• DALTER TABLE people ADD CONSTRAINT check_age CHECK (ABS(age)>=0);

• A
  13% (2)
• B
  7% (1)
• C
  7% (1)
• D
  73% (11)

Explanation

Option D is the only choice that applies a CHECK constraint directly to the table, which is SQL's built-in mechanism for enforcing data validation rules on insert and update operations. A CHECK constraint rejects any row where the condition evaluates to false, making it the appropriate tool for restricting column values. Note that ABS(age) >= 0 is mathematically always true (absolute values are never negative), so the intended condition should likely be age >= 0 - but among the given options, D is the only one using the correct structural approach.

Why the distractors fail:

• A & C (DELIMITER //) are identical MySQL directives that simply change the statement delimiter for defining stored procedures or triggers - they do nothing to table structure or data validation.
• B uses ADD COLUMN ... GENERATED ALWAYS, which creates a computed column that derives a value from existing data; it does not block invalid data from entering the table in the first place.

Memory tip: Think of a CHECK constraint as a bouncer - it stands at the door and refuses entry to any row that doesn't meet the condition. GENERATED columns are more like a calculator inside the club; they react to what's already there but don't control who gets in.

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