多选题Which two statements are true regarding views?（）AA subquery that defines a view cannot include the GROUP BY clauseBA view that is created with the subquery having the DISTINCT keyword can be updatedCA view that is created with the subquery having the p

第1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2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.

第3题：

第4题：

Which best describes an inline view?（）

• A、a schema object
• B、a subquery that can contain an ORDER BY clause
• C、another name for a view that contains group functions
• D、a subquery that is part of the FROM clause of another query

第5题：

Which two statements are true regarding subqueries? （）

• A、A subquery can retrieve zero or more rows 
• B、Only two subqueries can be placed atone level 
• C、A subquery can be used only in SQL query statements 
• D、A subquery can appear on either side of a comparison operator 
• E、There is no limit on the number of subquery levels in the WHERE clause of a SELECT statement 

第6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7题：

Which three statements about subqueries are true?（）

• A、A single row subquery can retrieve only one column and one row.
• B、A single row subquery can retrieve only one row but many columns.
• C、A multiple row subquery can retrieve multiple rows and multiple columns.
• D、A multiple row subquery can be compared by using the ">" operator.
• E、A single row subquery can use the IN operator.
• F、A multiple row subquery can use the "=" operator.

第8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9题：

Which two statements about subqueries are true?（）

• A、A single row subquery can retrieve data from only one table.
• B、A SQL query statement cannot display data from table B that is referred to in its subquery, unless table B is included in the main query's FROM clause.
• C、A SQL query statement can display data from table B that is referred to in its subquery, without including table B in its own FROM clause.
• D、A single row subquery can retrieve data from more than one table.
• E、A single row subquery cannot be used in a condition where the LIKE operator is used for comparison.
• F、A multiple-row subquery cannot be used in a condition where the LIKE operator is used for comparison.

第10题：

Which two statements about views are true?（）

• A、A view can be created as read only.
• B、A view can be created as a join on two or more tables.
• C、A view cannot have an ORDER BY clause in the SELECT statement.
• D、A view cannot be created with a GROUP BY clause in the SELECT statement.
• E、A view must have aliases defined for the column names in the SELECT statement.