题目: 设有关系SC(SNO,CNO,GRADE),主码是(SNO,CNO)。遵照实体完整性规则A.只有SNO不能取空值B.只有CNO不能取空值C.只有GRADE不能取空值D.SNO与CNO都不能取空值 答案: 参考答案:D
题型:选择题 Shanghai is bigger than _____ in Jiangsu and bigger than _______ in China.A.any city; any cityB.any city; any other cityC.any other city; the other citiesD.any other city; any city 查看答案