题目内容
在SQL Server 2000中，有学生表(学号，姓名，年龄，所在系)，学号是主码。在这个表上建有视图V1,V1视图的定义语句为： CREATE VIEW V1 AS SELECT姓名，年龄，所在系FROM学生表 WHERE年龄＞=(SELECT AVG(年龄)FROM学生表) 有下列操作语句： Ⅰ.UPDATE V1 SET年龄=年龄+1 Ⅱ.SELECT*FROM V1 WHERE年龄＞20 Ⅲ.DELETE FROM V1 WHERE年龄＞20 Ⅳ.INSERT INTO V1 VALUES(，张三，20,‘计算机系’) 以上语句能正确执行的是
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Some experimental evidence tends to show that alcohol reduces fear in an approach-avoidance situation. Conger trained one group of rats to approach a food goal and trained another group to avoid electric shock. After an injection of alcohol the pull away from the shock was measurably weaker, while the pull toward food was unchanged.
The obvious troubles experienced by alcoholic persons appear to contradict the learning theory in the explanation of alcoholism. The discomfort, pain, and punishment they experience should presumably discourage the alcoholics from drinking. The fact that alcoholic persons continue to drink in the face of family discord, loss of job, and illness is explained by the proximity of the drive of reduction to the consumption of alcohol; that is, alcohol has the immediate effect of reducing tension while the unpleasant consequences of drunken behavior. came only later. The learning pattern, therefore, favors the establishment and repetition of the resort to alcohol.
In fact, the anxieties and feelings of guilt caused by the consequences of excessive alcohol drinking may themselves become the signal for another time of alcohol abuse. The way in which the desire for another drink could be caused by anxiety is explained by the process of stimulus generalization: conditions or events securing at the time of reinforcement tend to acquire all the features of stimuli. When alcohol is consumed in association with a state of anxiety or leer, the emotional state itself takes on the properties of a stimulus, thus triggering another time of drinking.
The role of punishment is becoming increasingly important in explaining a cause of alcoholism based on the principles of learning theory. While punishment may serve to suppress a response, experiments have shown that in some cases it can serve as a reward and reinforce the behavior. Thus if the alcoholic person has learned to drink under conditions of both reward and punishment, either type of condition may trigger renewed drinking.
Conger's experiment with two groups of rats
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