問題文
A salary grade table holds a lowest value and a highest value for each grade. A query must attach the matching grade to every employee. Which kind of join condition does this need?
選択肢
- A non-equijoin that tests whether the salary falls between the two bounds of a grade row, because no column of the two tables holds equal values.
- A cross join that pairs every employee with every grade row, because the grade that applies is decided after the two tables have been combined.
- An equijoin that tests whether the salary equals the lowest bound of a grade row, because a join condition compares two columns for equality.
- A natural join that relies on the columns that carry the same name in the two tables, because the grade table repeats the name of the salary column.