フリー問題

問題文

A reviewer looks at a gateway table where one column must name each row and the rest may be left blank. Which pair separates what the primary key does from what the ordinary column does?

選択肢

1. The table relies on one column that can name the row, so the primary key borrows the unique value and the ordinary column allows the empty cell in that schema documentation.
2. The table relies on one column that can name the row, so the primary key borrows the unique value and the ordinary column populates the empty cell in that schema documentation.
3. The table relies on one column that can name the row, so the primary key enforces the unique value and the ordinary column populates the empty cell in that schema documentation.
4. The table relies on one column that can name the row, so the primary key enforces the unique value and the ordinary column allows the empty cell in that schema documentation.