フリー問題

問題文

A query computes salary + commission_pct * salary as the total for every employee. Some employees hold a null commission_pct. What appears in that computed column for those employees?

選択肢

1. A null appears in the column, because an arithmetic operator that receives a null operand produces a null result for the whole expression.
2. An error appears while the row is fetched, because an arithmetic operator rejects a null operand as it evaluates the expression for that row.
3. A zero appears in the column, because an arithmetic operator reads a null operand as the number zero before it evaluates the expression.
4. The salary appears in the column, because an arithmetic operator skips a null operand and keeps evaluating the rest of the expression.