多选题Which three statements are true regarding subqueries?（）ASubqueries can contain GROUP BY and ORDER BY clausesBMain query and subquery can get data from different tablesCMain query and subquery must get data from the same tablesDSubqueries can contain OR

第1题：

Which two statements are true regarding the USING clause in table joins?（）

• A、It can be used to join a maximum of three tables 
• B、It can be used to restrict the number of columns used in a NATURAL join 
• C、It can be used to access data from tables through equijoins as well as nonequijoins 
• D、It can be used to join tables that have columns with the same name and compatible data types

第2题：

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

第3题：

第4题：

Which two statements about subqueries are true? （）

• A、A subquery should retrieve only one row.
• B、A subquery can retrieve zero or more rows.
• C、A subquery can be used only in SQL query statements.
• D、Subqueries CANNOT be nested by more than two levels.
• E、A subquery CANNOT be used in an SQL query statement that uses group functions.
• F、When a subquery is used with an inequality comparison operator in the outer SQL statement, the column list in the SELECT clause of the subquery should contain only one column.

第5题：

Which  statements are true regarding a tablespace（）

• A、It can span multiple databases.
• B、It can consist of multiple data files.
• C、It can contain blocks of different sizes.
• D、It can contain segments of different sizes.
• E、It can contain a part of a nonpartitioned segment

第6题：

Which three statements are true about terms in a policy?（）

• A、The order of the terms in a policy is irrelevant
• B、The action is specified in a then statement
• C、Ters are optional in a policy
• D、The match condition can be identified with a from statement
• E、Every policy must contain at least one term

第7题：

Which two statements are true regarding views?（）

• A、A subquery that defines a view cannot include the GROUP BY clause 
• B、A view that is created with the subquery having the DISTINCT keyword can be updated 
• C、A view that is created with the subquery having the pseudo column ROWNUM keyword cannot be updated 
• D、A data manipulation language (DML) operation can be performed on a view that is created with the subquery having all the NOT NULL columns of a table

第8题：

第9题：

Which statements are true regarding the Query Result Cache？（） 

• A、 It can be set at the system， session， or table level.
• B、 It is used only across statements in the same session.
• C、 It can store the results from normal as well as flashback queries.
• D、 It can store the results of queries based on normal，temporary，and dictionary tables.

第10题：

Which three statements about subqueries are true? （）

• A、A main query can have more than one subquery.
• B、A subquery can have more than one main query.
• C、The subquery and main query must retrieve data from the same table.
• D、The subquery and main query can retrieve data from different tables.
• E、Only one column or expression can be compared between the subquery and main query.
• F、Multiple columns or expression can be compared between the subquery and main query.