【单选题】
有关系：教师(编号，姓名，生日，职称)，从关系中查询所有教授的情况应使用___关系运算。
A. 投影
B. 选择
C. 连接
D. 笛卡儿积
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答案
B
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相关试题
【单选题】
有关系：销售(商品号，推销员编号，销售日期，客户名)，那么，该关系的主键是___。
A. 商品号
B. 商品号，推销员编号
C. (商品号，推销员编号，销售日期)
D. (商品号,推销员编号,销售日期,客户名)
【单选题】
有关系：教学(学号、教工号、课程号),每个学生可以选修多门课程，每门课程可以由多名学生来选修，每个老师可以讲授多门课程，每门课程可以由多个老师来讲授，那么该关系的主键是___。
A. 课程号
B. 教工号
C. (学号，教工号，课程号)
D. (学号，教工号)
【单选题】
如果表S(A,B,C)中，设置A为主键，当向S表插入一行新数据时，该行___。
A. A,B,C属性的值都可以与已有的行相同
B. A,B,C属性的值都不能与已有的行相同
C. A属性的值不能与已有的行相同，但允许为空
D. A属性的值不能与已有的行相同，也不能为空
【单选题】
在SQL Server的以下数据类型中，最适合表示一个人的体重(公斤,保留一位小数)的是___。
A. char
B. float
C. tinyint
D. numeric
【单选题】
对于数据库中的表A，如果想要清空A中的数据且不留下事务日志，应使用___。
A. DELETE TABLE A
B. DROP TABLE A
C. ALTER TABLE A
D. TRUNCATE TABLE A
【单选题】
对工资表（员工号，姓名，部门号，月薪）进行查询，分部门统计人数和平均工资，查询语句应使用___。
A. SELECT 部门号，Count(*),AVG(月薪) FROM 工资表 GROUP BY 月薪
B. SELECT 姓名，Count(*),AVG(月薪) FROM 工资表 GROUP BY 部门号
C. SELECT 部门号，Count(月薪),AVG(*) FROM 工资表 GROUP BY 部门号
D. SELECT 部门号，Count(月薪),AVG(月薪) FROM 工资表 GROUP BY 部门号
【单选题】
学生成绩表grade中有字段score（float），现要把所有在55-60之间的分数提高5分，以下语句正确的是___
A. update grade set score=score+5 where score in 55…60
B. update grade set score=score+5 where score>=55 and score<=60
C. update grade set score=score+5 where score between 55 or 60
D. update grade set score=score+5 where score<=55 and score>=60
【单选题】
对于索引，以下说法正确的是___。
A. 一个数据表只能有一个索引
B. 一个数据表只能有一个唯一索引
C. 一个数据表只能有一个聚集索引
D. 一个数据标只能有一个非聚集索引
【单选题】
下列关于索引的描述不正确的是___
A. 索引是一个指向表中数据的指针
B. 索引是在元组上建立的一种数据库对象
C. 索引的建立和删除对数据毫无影响
D. 表被删除时将同时删除表上建立的索引
【单选题】
在创建表的同时，可以用___ 来创建唯一性索引
A. 设置主键约束或唯一约束
B. create table ，create index
C. create index
D. 都可以
【单选题】
如果有两个事务同时对数据库中同一数据进行操作，不会引起冲突的是___。
A. 一个DELETE和一个SELECT
B. 一个SELECT和一个DELETE
C. 两个UPDATE
D. 两个SELECT
【单选题】
当触发器执行时，系统会创建临时表保存用户操作更改的行的新值和旧值， UPDATE操作所涉及的值会被临时保存在___。
A. updated表
B. inserted 表
C. deleted表
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推荐试题
【单选题】
A vSphere content library administrator is attempting to unpublish the content library, but the option is grayed out as shown in the Exhibit. Which statement identifies the reason for not being able to unpublish? ___
A. The content library is optimized for syncing over HTTP.
B. A synchronization operation is in progress with this content library.
C. There are active subscriptions on this content library.
D. Underlying storage for this content library is not accessible.
【单选题】
Assuming a mirrored (RAID-1) object configuration, how many hosts must contribute storage in a non-stretched VMware vSAN cluster to satisfy the “Number of failures to tolerate” policy option?“n” is the desired “Number of failures to tolerate” value for all options.___
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【单选题】
An administrator must change the statistics level for short-term performance monitoring and wants to collect metrics for all counters, excluding minimum and maximum rollup values. What would be the statistics level?___
A. Level 3
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C. Level 2
D. Level 4
【单选题】
In a vSphere environment, two resource pools are created as shown in the Exhibit. Each VM is configured with 1 GB of memory. When the administrator tried to power on VM3, the operation failed. What action in the resource pool settings will allow VM3 to power on successfully?___
A. Deselect Expandable Memory Reservation
B. Increase Memory Reservation
C. Deselect Expandable CPU Reservation
D. Increase the CPU Reservation
【单选题】
Which network is used by vSphere HA when VMware vSAN is enabled?___
A. Management network
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C. vMotion network
D. VSAN network
【单选题】
Which statement is correct when migrating from a Windows vCenter Server to the vCenter Server Appliance 6.5?___
A. Migration deployments do not migrate local OS users from the source vCenter Server.
B. Migration deployments support DHCP on the source vCenter Server.
C. Migration deployments allow the source vCenter Server to remain powered on afterwards.
D. Migration deployments support custom ports for all services on the source vCenter Server.
【单选题】
How can failback of a recovered virtual machine in vSphere Replication be performed?___
A. No action required, because failback is automatically performed to the source site.
B. Configure a new replication in the reverse direction at the target site.
C. Disable or Stop the virtual machine replication on the source site.
D. Power off and unregister the virtual machine on the target site.
【单选题】
After upgrading the vSphere infrastructure and VMware Tools to version 6.5, the “Upgrade VM Compatibility” option is grayed out in the vSphere Web Client. (See Exhibit.) What must the administrator do to enable the VM compatibility upgrade?___
A. VMware Tools should be upgraded last.
B. Restart the ESXi server.
C. Uninstall VMware Tools.
D. Power off the virtual machine.
【单选题】
What availability mode does vCenter HA provide?___
A. Active-Passive
B. Active-Standby
C. Active-Active
D. Load-balanced
【单选题】
In which scenario will vSphere DRS balance resources when set to Fully Automated?___
A. Hosts with only shared storage
B. Hosts are part of a vSphere HA cluster
C. Power Management is set to Balanced on hosts
D. Hosts with shared or non-shared storage
【单选题】
What VMware technology can be used to move physical servers to the vSphere infrastructure?___
A. VMware vMotion
B. VMware Converter
C. VMware vCenter Server
D. OVF transport
【单选题】
Upgrading vCenter Server with Microsoft SQL database fails with the following error message: The DB User entered does not have the required permissions needed to install and configure vCenter Server with the selected DB. Please correct the following error(s): %sWhat could cause this error?___
A. incorrect ports open on SQL Server
B. incorrect database on the SQL server
C. incorrect compatibility mode on the SQL server
D. incorrect permission on SQL Server database
【单选题】
What is a potential downside of having more than four paths per datastore?___
A. limits the storage protocols
B. increases storage latency for VM
C. limits the path selection policies
D. limits the number of LUNs per host
【单选题】
Which feature facilitates the sharing of templates via vCenter Server?___
A. Content Library
B. OVF
C. folders
D. vApp
【单选题】
A vSphere Administrator is in the process of configuring replication for a virtual machine, but is not able to select the Recovery Point Objective (RPO) value of 5 minutes. Which statement could explain why the RPO value cannot be lower than 15 minutes?___
A. The OS quiescing option is selected for Replication options.
B. The virtual machine hardware version is not compatible.
C. The target and source sites use different types of datastores.
D. The target and source sites are not using VMFS 6.0 datastore.
【单选题】
What advanced parameter defines a custom isolation IP address for a vSphere HA cluster?___
A. das.usedefaultisolationaddress
B. das.isolationshutdowntimeout
C. fdm.isolationpolicydelaysec
D. das.isolationaddress
【单选题】
Which method is supported for backing up the virtual machine that contains vCenter Server?___
A. differential
B. incremental
C. full image
D. individual disks
【单选题】
A vSphere Administrator must ensure that a user is able to view and manage the system configuration in vSphere Web Client. In the vCenter Single Sign-On domain, which group should the user be a part of?___
A. SystemConfiguration.BashShellAdministrators
B. ComponentManager. Administrators
C. Administrators
D. SystemConfiguration.Administrators
【单选题】
What is the minimum number of hosts that must contribute capacity to a non-ROBO single site VMware vSAN cluster?___
A. 1
B. 64
C. 3
D. 2
