OCP-1Z0-051-V9.02-135题

135. Which three statements are true regarding subqueries? (Choose three.)

A. Subqueries can contain GROUP BY and ORDER BY clauses. 对，可以包含group by 和order by

B. Main query and subquery can get data from different tables. 对，可以分别拿不同表的数据

C. Main query and subquery must get data from the same tables. 错。看B选项

D. Subqueries can contain ORDER BY but not the  GROUP BY clause. 错，看A选项

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.

Answer: ABF

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12879585

A,子查询可以包含GROUP BY和ORDER BY子句

B,主查询和子查询能从不同的表里获取数据

C,主查询和子查询必须从同一个表获取数据,错误，可以从不同表获取数据

D,子查询能包含ORDER BY 子句，但是不能包含GROUP BY子句,错误，可以包含GROUP BY子句

E,主查询与子查询之间只能比较一个列或一个表达式，错误，可以比较多行，使用any，all等

F,主查询与子查询之间可以比较多个列或多个表达式.