在关系代数的连接操作中,连接操作需要取消重复列的是( )。A.自然连接 B.笛卡尔

题型:单项选择题

问题:

在关系代数的连接操作中,连接操作需要取消重复列的是( )。

A.自然连接

B.笛卡尔积

C.等值连接

D.θ连接

考点:计算机等级考试数据库技术三级数据库技术笔试331
题型:单项选择题

We know health and happiness are important in everyone’s life. Here are some ways to make them easy.

Eat a balanced diet(平衡饮食). Eat a lot of fruit and vegetables, some grains(谷物) and a little meat.

Exercise twice or three times a week.

Get enough sleep. It is best to get eight hours’ sleep a day.

Keep yourself busy. This is good because it stops you from having bad habits. To keep yourself busy, you can walk around the house, spend time with your pets, do a sport, or do a hobby you enjoy.

Go out and make friends. Spend time and have fun with them. Talk with them, but you must be sure not to talk about anything bad. You should stay with the people who are healthy and happy themselves.

小题1:How often should you exercise if you want to get health and happiness?

A.Every day .

B.Twice a day

C.Twice or three times a week .

D.Three times a month.小题2:How many hours do you need to sleep every day?

A.Seven.

B.Eight.

C.Nine.

D.Ten小题3:The underlined word “it”referes to (指的是)“     ”.

eating a balanced diet.  B.exercising more  C. keeping yourself busy  D.making friends

小题4:Whice of the following is NOT true?

A.We should eat a lot of meat to keep healthy.

B.We should exercise to keep healthy.

C.The people whom we make friends with must be healthy and happy themselves.

D.We can spend our free time doing a sport or doing hobby we enjoy.小题5:Which is the best title(标题) for the passage?

A.Eating Habit

B.Healthy Lifestyle

C.Making friends

D.Ways to Have Health and Happines

题型:单项选择题
如果实数a≠b满足(a+1)2=3-3(a+1),3(b+1)=3-(b+1)2,那么
a
b
+
b
a
的值为______.
题型:单项选择题

统计管理相对人对大连市统计局做出的具体行政行为不服,申请复议的,可以向()提出。

A.辽宁省统计局

B.大连市人民政府

C.辽宁省人民政府

D.国家统计局

E.大连市人民政府法制局

题型:单项选择题

历史学家不离事而言理,客观精神乃是历史写作的第一守则。在描写一个历史事件时,下列哪一项最不易受到历史学家主观因素的影响

A.事件发生的时地

B.事件的前因后果

C.事件的历史意义

D.事件的是非评价

题型:单项选择题

经采取所有法律部门认可的措施和实施必要的追偿、索赔程序后,符合下列哪个条件的,不可申请损失核销()

A.在ATM机处理日常业务过程中发生的短款、误收假币以及发生其他意外情况造成的损失

B.交易对手破产、撤销或关闭后,中国农业银行根据交易有关协议行使终止交易权利并履行法律程序,确认无法收回的净债权

C.取得受偿物品或资金,但未进行处置并冲抵损失的

D.固定资产盘亏、提前报废、毁损,转销的账面净值在扣除残料收入和获得保险公司以及责任人赔偿后形成的净损失

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