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【判断题】
CW7800系列的管脚下如图所示,1脚是输入端,2脚是输出端,3脚是输出端。A.
正确
B.
错误
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【简答题】请简述流行病学的主要应用
【简答题】简述流行病学的主要应用领域。
【单选题】A view is created with the following statement:CREATE VIEW v1 AS SELECT col1, col2, col3, col4 FROM t1 WHERE col4 > 1000 WITH CHECK OPTIONWhat is the effect of the CHECK OPTION clause?（）
A.
Any row inserted or updated through view V1 must meet the condition that col4 > 1000.
B.
From now on, any row inserted or updated in table T1 must meet the condition that col4 > 1000, but existing rows in the table are not checked.
C.
At view creation, DB2 will check the data in table T1, and if in any row doesn't meet the condition col4 > 1000, the view creation will be rejected.
D.
Any row inserted or updated through view V1 must meet the condition that col4 > 1000 and no row in table T1 can be updated such that col4 <= 1000, but new rows in the table can be inserted with col4 <=1000.
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