更多相关问题在同一个数据库中某个关系R1中的属性或属性组若在另一个关系R2中作为关键字（主码）使用，则该属性或属性组为R1的___________。Some psychologists find out that some girls couldn’t know the ways and directions which are related to their ______ when they are young。（3）((A+B+C) CD)+(B+C)(ABD+BC)
更多相关问题在同一个数据库中某个关系R1中的属性或属性组若在另一个关系R2中作为关键字（主码）使用，则该属性或属性组为R1的___________。Some psychologists find out that some girls couldn’t know the ways and directions which are related to their ______ when they are young。（3）((A+B+C) CD)+(B+C)(ABD+BC)