设关系R、S、W各有10个元组,那么这3个关系自然连接的元组个数为() ["10","30","1000","不确定(与计算结果有关)"]
在关系中,"基数"(Cardinality)是指() ["行数","属性个数","关系个数","列数"]
在关系中,"元数"(Arity)是指() ["行数","元组个数","关系个数","列数"]
为什么X封锁需保留到事务终点,而S封锁可随时解除?
COMMIT操作和检查点时的操作有什么联系?你认为应该如何恰当地协调这两种操作才有利于DB的恢复?
日志文件中记载了哪些内容?