In relation schema R, XY means that .
A、InoneofR’srelation,iftherearetworowsthatequalonX,thentheyalsoequalonY.
B、IneachofR’srelation,iftherearetworowsthatequalonX,thentheyalsoequalonY.
C、InoneofR’srelation,valuesofYequalvaluesofX.
D、IneachofR’srelation,valuesofYequalvaluesofX.
发布时间：2025-10-14 06:20:49
