Inserts the keyword NATURAL into the SQL statement that defines the relation. The relation joins all columns that have the same column name in both tables. The resulting joined table contains only one column for each pair of equally named columns.
把关键字 NATURAL 插入到定义了关系的 SQL 语句中。该关系把两个表中所有具有相同列名称的列连接起来。生成的连接表对每对命名相同的列都只保留一列。