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 subquer

第1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2题：

Which two statements are true about a job chain?（）

• A、A job chain can contain a nested chain of jobs.
• B、The jobs in a job chain cannot have more than one dependency.
• C、A job of the CHAIN type can be run using event-based or time-based schedules.
• D、The jobs in a job chain can be executed only by using the events generated by the Scheduler

第3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4题：

Which two statements are true about a job chain? （）(Choose two.)

• A、A job chain can contain a nested chain of jobs.
• B、The jobs in a job chain cannot have more than one dependency.
• C、A job of the CHAIN type can be run using event-based or time-based schedules.
• D、The jobs in a job chain can be executed only by using the events generated by the Scheduler

第5题：

Which three statements are true regarding single-row functions？（）

• A、 They can accept only one argument.
• B、 They can be nested up to only two levels.
• C、 They can return multiple values of more than one data type.
• D、 They can be used in SELECT， WHERE， and ORDER BY clauses.  
• E、 They can modify the data type of the argument that is referenced.
• F、 They can accept a column name， expression， variable name， or a user-supplied constant as arguments.

第6题：

Which two statements are true about a job chain？（）

• A、 A job chain can contain a nested chain of jobs
• B、 The jobs in a job chain cannot have more than one dependency
• C、 A job of the CHAIN type can be run using event-based or time-based schedules
• D、 The jobs in a job chain can be executed only by using the events generated by the Scheduler

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第13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14题：

You define a multiple-row subquery in the WHERE clause of an SQL query with a comparison operator "=". What happens when the main query is executed? （）

• A、The main query executes with the first value returned by the subquery.
• B、The main query executes with the last value returned by the subquery.
• C、The main query executes with all the values returned by the subquery.
• D、The main query fails because the multiple-row subquery cannot be used with the comparison operator.
• E、You cannot define a multiple-row subquery in the WHERE clause of a SQL query.

第15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16题：

Which two statements are true about simple views？（）

• A、Views can be created as read only.
• B、Views are data segments like tables.
• C、Views can be created on the basis of more than one table.
• D、Data manipulation language （DML） operations cannot be performed on views.

第17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 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 an INSERT statement to insert multiple rows at a time.

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