ocp考试题库下载：11g-v9.02-051-139题
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139. Which three statements are true about multiple-row subqueries? (Choose three.)
A. They can contain a subquery within a subquery.
B. They can return multiple columns as well as rows.
C. They cannot contain a subquery within a subquery.
D. They can return only one column but multiple rows.
E. They can contain group functions and GROUP BY and HAVING clauses.
F. They can contain group functions and the GROUP BY clause, but not the HAVING clause.
Answer: ABE
试题解析：
A,子查询中能包含子查询,可以嵌套，但最多255层。
B，能返回多列和多行，正确。
C，子查询中不能包含子查询，错误，子查询可以嵌套
D，只能返回一列多行，错误，可以返回多行多列
E，可以包含组函数和GROUP BY,HAVING子句，正确
F，可以包含组函数和GROUP BY，但不能包含HAVING子句，错误，是可以包含HAVING子句的。
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