皮皮学，免费搜题
登录
搜题
【单选题】
下列对主关键字（也称主键）的叙述，错误的是
A.
作为主关键字的字段中不许有重复值和空值
B.
主关键字的字段值是唯一的
C.
主关键字可以是一个字段 , 也可以是一组字段
D.
数据库中的每个表都必须有一个主关键字
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
.
..
皮皮学刷刷变学霸
举一反三
【单选题】A: What did the doctor do?B: Well, first she really helped me to understand the __________ of Yin and Yang. I just always thought that was something you get a tattoo (纹身) of when you're in college.
A.
methods
B.
definition
C.
concept
D.
measures
查看完整题目与答案
【多选题】以下选项中,关于斜导柱抽芯机构装配要求说法不正确的是( )。
A.
滑块上的斜导柱孔口为圆环状
B.
滑块上的斜导柱孔口为圆形
C.
斜导柱外侧与滑块斜导柱孔应留有一定间隙
D.
斜导柱外侧与滑块斜导柱孔不留间隙
E.
闭模后滑块的上平面与定模底面应留有一定间隙
查看完整题目与答案
【单选题】Steve introduced me to the doctor ______ had helped him out when he was faced with mental stress.
A.
who
B.
whom
C.
that
D.
which
查看完整题目与答案
【简答题】support sound respond consult reply impressive assume false encourage solve 1. I will­­­ ­­­_____ to this text message when I have time. 2. The claim t...
查看完整题目与答案
【单选题】斜导柱抽芯机构装配要求闭模后,斜导柱外侧与滑块斜导柱孔留有( )的间隙。
A.
0.05～0.1mm
B.
0.1～0.2mm
C.
0.2～0.5mm
D.
0.5～1.0mm
查看完整题目与答案
【单选题】以下选项中,关于斜导柱抽芯机构装配要求说法正确的是( )。
A.
斜导柱外侧与滑块斜导柱孔不留间隙
B.
闭模后滑块的上平面与定模底面齐平
C.
滑块上的斜导柱孔口为圆形
D.
斜导柱外侧与滑块斜导柱孔留有0.2～0.5mm的间隙
查看完整题目与答案
【简答题】阅读以下请假条,然后填空 Oct. 18 Dear Miss Gao, I'm sorry I can't go to school today. I helped the farmers pick apples with my classmates on the farm yesterday. Unluckily, I fell off the ladder and hurt my leg, b...
查看完整题目与答案
【单选题】—How long have you known the doctor ? — he helped me three years ago.
A.
When
B.
Before
C.
Because
D.
Since
查看完整题目与答案
【单选题】The doctor suggested supplement ing my diet with vitamins E and A.
A.
The government provided an additional £25 million to expand the service.
B.
Our youngest son helped me make some long-overdue improvement s on the ourdoor toilet.
C.
Our hens keep us in eggs.
D.
Our freezer filled up with cherries.
查看完整题目与答案
【简答题】编写程序实现10个 元素数组分别赋值1,2,3,4,5,6,7,8,9,10,之后逆序输出。输出格式为10 9 8 7 6 5 4 3 2 1 要求输出显示为:
查看完整题目与答案
相关题目：
【单选题】A: What did the doctor do?B: Well, first she really helped me to understand the __________ of Yin and Yang. I just always thought that was something you get a tattoo (纹身) of when you're in college.
A.
methods
B.
definition
C.
concept
D.
measures
查看完整题目与答案
【多选题】以下选项中,关于斜导柱抽芯机构装配要求说法不正确的是( )。
A.
滑块上的斜导柱孔口为圆环状
B.
滑块上的斜导柱孔口为圆形
C.
斜导柱外侧与滑块斜导柱孔应留有一定间隙
D.
斜导柱外侧与滑块斜导柱孔不留间隙
E.
闭模后滑块的上平面与定模底面应留有一定间隙
查看完整题目与答案
【单选题】Steve introduced me to the doctor ______ had helped him out when he was faced with mental stress.
A.
who
B.
whom
C.
that
D.
which
查看完整题目与答案
【简答题】support sound respond consult reply impressive assume false encourage solve 1. I will­­­ ­­­_____ to this text message when I have time. 2. The claim t...
查看完整题目与答案
【单选题】斜导柱抽芯机构装配要求闭模后,斜导柱外侧与滑块斜导柱孔留有( )的间隙。
A.
0.05～0.1mm
B.
0.1～0.2mm
C.
0.2～0.5mm
D.
0.5～1.0mm
查看完整题目与答案
【单选题】以下选项中,关于斜导柱抽芯机构装配要求说法正确的是( )。
A.
斜导柱外侧与滑块斜导柱孔不留间隙
B.
闭模后滑块的上平面与定模底面齐平
C.
滑块上的斜导柱孔口为圆形
D.
斜导柱外侧与滑块斜导柱孔留有0.2～0.5mm的间隙
查看完整题目与答案
【简答题】阅读以下请假条,然后填空 Oct. 18 Dear Miss Gao, I'm sorry I can't go to school today. I helped the farmers pick apples with my classmates on the farm yesterday. Unluckily, I fell off the ladder and hurt my leg, b...
查看完整题目与答案
【单选题】—How long have you known the doctor ? — he helped me three years ago.
A.
When
B.
Before
C.
Because
D.
Since
查看完整题目与答案
【单选题】The doctor suggested supplement ing my diet with vitamins E and A.
A.
The government provided an additional £25 million to expand the service.
B.
Our youngest son helped me make some long-overdue improvement s on the ourdoor toilet.
C.
Our hens keep us in eggs.
D.
Our freezer filled up with cherries.
查看完整题目与答案
【简答题】编写程序实现10个 元素数组分别赋值1,2,3,4,5,6,7,8,9,10,之后逆序输出。输出格式为10 9 8 7 6 5 4 3 2 1 要求输出显示为:
查看完整题目与答案