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Which three statements are true regarding subqueries?（）
A:Subqueries can contain GROUP BY and ORDER BY clauses 
B:Main query and subquery can get data from different tables 
C:Main query and subquery must get data from the same tables 
D:Subqueries can contain ORDER BY but not the GROUP BY clause 
E:Only one column or expression can be compared between the main query and subquery
F: Multiple columns or expressions can be compared between the main query and subquery

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出自：Oracle认证

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