单选题在关系中,"基数"(Cardinality)是指()A行数B属性个数C关系个数D列数
单选题
在关系中,"基数"(Cardinality)是指()
A
行数
B
属性个数
C
关系个数
D
列数
参考解析
解析:
暂无解析
相关考题:
下面对cardinality的最佳描述是:()A、在geodatabase中空间数据和属性数据之间的联合B、描述相互关联的两种类型的数量或对象之间的关系C、在一个连接中,主键字段和名称字段之间的联系D、在geodatabase中,用来描述不同主键值数量的表的属性
Examine the parameters for your database instance: Which three statements are true about the process of automatic optimization by using cardinality feedback?()A、The optimizer automatically changes a plan during subsequent execution of a SQL statement if there is a huge difference in optimizer estimates and execution statistics.B、The optimizer can re optimize a query only once using cardinality feedback.C、The optimizer enables monitoring for cardinality feedback after the first execution of a query.D、The optimizer does not monitor cardinality feedback if dynamic sampling and multicolumn statistics are enabled.E、After the optimizer identifies a query as a re-optimization candidate, statistics collected by thecollectors are submitted to the optimizer.
多选题Examine the parameters for your database instance: Which three statements are true about the process of automatic optimization by using cardinality feedback?()AThe optimizer automatically changes a plan during subsequent execution of a SQL statement if there is a huge difference in optimizer estimates and execution statistics.BThe optimizer can re optimize a query only once using cardinality feedback.CThe optimizer enables monitoring for cardinality feedback after the first execution of a query.DThe optimizer does not monitor cardinality feedback if dynamic sampling and multicolumn statistics are enabled.EAfter the optimizer identifies a query as a re-optimization candidate, statistics collected by thecollectors are submitted to the optimizer.