问题 单项选择题

~(35)题使用如下的“仓库”表和“职工”表,表结构如下:
仓库(仓库号C(3)、所在地C(8)、人数N(2))
职工(仓库号C(3)、职工号C(2)、姓名C(8)、工资I)

检索至少有一名职工信息的“仓库号”及仓库的“所在地”和“人数”,正确的SQL命令是( )。

A.SELECT仓库号,所在地,人数FROM仓库WHERE IN; (SELECT仓库号FROM职工WHERE仓库号=职工.仓库号)

B.SELECT仓库号,所在地,人数FROM仓库WHERE仓库号IN; SELECT仓库号FROM职工WHERE仓库号=仓库.仓库号

C.SELECT仓库号,所在地,人数FROM仓库WHERE NOT EXISTS; (SELECT仓库号.FROM职工WHERE仓库号=仓库.仓库号)

D.SELECT仓库号,所在地,人数FROM仓库WHERE:EXISTS; (SELECT仓库号FROM职工WHERE仓库号=仓库.仓库号)

答案

参考答案:D

解析: 本题中EXISTS属于SQL查询谓词,EXISTS或NOT EXISTS是用来检查在子查询中是否有结果返回,即存在元组或不存在元组,子查询要用圆括号括起来。选项D) 的SQL查询中的子查询查询的是“职工”表中“仓库号”等于“仓库”表中“仓库号”的数据,然后在外层查询中检索“仓库”表中的“仓库号”是否存在于子查询的查询结果中,将存在的“仓库号”显示其“仓库号”、“所在地”和“人数”的信息。

单项选择题

A deal is a deal—except, apparently, when Entergy is involved. The company, a major energy supplier in New England, provoked justified outrage in Vermont last week when it announced it was reneging on a longstanding commitment to abide by the state’s strict nuclear regulations.

Instead, the company has done precisely what it had long promised it would not challenge the constitutionality of Vermont’s rules in the federal court, as part of a desperate effort to keep its Vermont Yankee nuclear power plant running. It’s a stunning move.

The conflict has been surfacing since 2002, when the corporation bought Vermont’s only nuclear power plant, an aging reactor in Vernon. As a condition of receiving state approval for the sale, the company agreed to seek permission from state regulators to operate past 2012. In 2006, the state went a step further, requiring that any extension of the plant’s license be subject to Vermont legislature’s approval. Then, too, the company went along.

Either Entergy never really intended to live by those commitments, or it simply didn’t foresee what would happen next. A string of accidents, including the partial collapse of a cooling tower in 207 and the discovery of an underground pipe system leakage, raised serious questions about both Vermont Yankee’s safety and Entergy’s management—especially after the company made misleading statements about the pipe. Enraged by Entergy’s behavior, the Vermont Senate voted 26 to 4 last year against allowing an extension.

Now the company is suddenly claiming that the 2002 agreement is invalid because of the 2006 legislation, and that only the federal government has regulatory power over nuclear issues. The legal issues in the case are obscure: whereas the Supreme Court has ruled that states do have some regulatory authority over nuclear power, legal scholars say that Vermont case will offer a precedent-setting test of how far those powers extend. Certainly, there are valid concerns about the patchwork regulations that could result if every state sets its own rules. But had Entergy kept its word, that debate would be beside the point.

The company seems to have concluded that its reputation in Vermont is already so damaged that it has noting left to lose by going to war with the state. But there should be consequences. Permission to run a nuclear plant is a public trust. Entergy runs 11 other reactors in the United States, including Pilgrim Nuclear station in Plymouth. Pledging to run Pilgrim safely, the company has applied for federal permission to keep it open for another 20 years. But as the Nuclear Regulatory Commission (NRC) reviews the company’s application, it should keep in mind what promises from Entergy are worth.

The phrase "reneging on"(kine 3. para.1) is closest in meaning to()

A. condemning

B. reaffirming

C. dishonoring

D. securing

填空题