在VisualFoxPro中，如果要求所建立索引的字段值不允许重复，并且一个表中只能创建一个，这种索引应该是（　　）。

A、主索引

B、唯一索引

C、候选索引

D、普通索引

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  A、 Oracle uses statistical relevance to determine when an adaptive threshold has been breached for the metric.

  B、 The statistics for the metric values observed over the baseline time period are not examined to determine threshold values.

  C、 Oracle determines when an adaptive threshold has been breached based on the maximum value captured by the baseline.

  D、 The total concurrent number of threshold violations, which must occur before an alert is raised for the metric, has been set to zero.

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  B、心内注射

  C、心前区叩击

  D、清理呼吸道

  E、口对口人工呼吸

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  A、管理的科学性

  B、管理的自然属性

  C、管理的广泛性

  D、人和时间

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  A

  SELECT cust_last_name, cust_credit_limit FROM customers ORDER BY cust_credit_limit DESC

  B

  SELECT cust_last_name, cust_credit_limit FROM customers ORDER BY cust_credit_limit

  C

  SELECT cust_last_name, cust_credit_limit FROM customers ORDER BY cust_credit_limit NULLS LAST

  D

  SELECT cust_last_name, cust_credit_limit FROM customers ORDER BY cust_last_name, cust_credit_limit NULLSLAST

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• 胃十二指肠溃疡上腹部疼痛可表现为（）

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  B、转移性疼痛

  C、上腹饱胀

  D、压榨性痛

  E、上腹部疼痛伴窒息感

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