多选题Which two statements are true regarding the USING clause in table joins?（）AIt can be used to join a maximum of three tablesBIt can be used to restrict the number of columns used in a NATURAL joinCIt can be used to access data from tables through equijo

第1题：

Which two statements regarding asymmetric key encryption are true？（）

• A、The same key is used for encryption and decryption.
• B、It is commonly used to create digital certificate signatures.
• C、It uses two keys： one for encryption and a different key for decryption.
• D、An attacker can decrypt data if the attacker captures the key used for encryption

第2题：

Which two statements are true about WHERE and HAVING clauses? （）

• A、A WHERE clause can be used to restrict both rows and groups.
• B、A WHERE clause can be used to restrict rows only.
• C、A HAVING clause can be used to restrict both rows and groups.
• D、A HAVING clause can be used to restrict groups only.
• E、A WHERE clause CANNOT be used in a query of the query uses a HAVING clause.
• F、A HAVING clause CANNOT be used in subqueries.

第3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4题：

Which statements describe the capabilities of the DBMS_NETWORK_ACL_ADMIN package?（）

• A、It can be used to allow the access privilege settings for users but not roles.
• B、It can be used to allow the access privilege settings for users as well as roles.
• C、It can be used to control the time interval for which the access privilege is available to a user.
• D、It can be used to selectively restrict the access for each user in a database to different host computers.
• E、It can be used to selectively restrict a user's access to different applications in a specific host computer.

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 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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第13题：

What is true about joining tables through an equijoin?（）

• A、You can join a maximum of two tables through an equijoin.
• B、You can join a maximum of two columns through an equijoin.
• C、You specify an equijoin condition in the SELECT or FROM clauses of a SELECT statement.
• D、To join two tables through an equijoin, the columns in the join condition must be primary key and foreign key columns.
• E、You can join n tables (all having single column primary keys) in a SQL statement by specifying a minimum of n-1 join conditions.

第14题：

Which three tasks can be performed using regular expression support in Oracle Database 10g？（）

• A、 it can be used to concatenate two strings.
• B、 it can be used to find out the total length of the string.
• C、 it can be used for string manipulation and searching operations.
• D、 it can be used to format the output for a column or expression having string data.
• E、 it can be used to find and replace operations for a column or expression having string data.

第15题：

Which three are true?（）

• A、A MERGE statement is used to merge the data of one table with data from another.
• B、A MERGE statement replaces the data of one table with that of another.
• C、A MERGE statement can be used to insert new rows into a table.
• D、A MERGE statement can be used to update existing rows in a table.

第16题：

Which two statements regarding a SQL profile are true？（）

• A、 It is built by Automatic Tuning Optimizer.
• B、 It cannot be stored persistently in the data dictionary.
• C、 It can be used by the query optimizer automatically.
• D、 It can be created manually by using the CREATE PROFILE command.

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 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18题：

Which two statements are true regarding the USING and ON clauses in table joins?（）

• A、Both USING and ON clauses can be used for equijoins and nonequijoins 
• B、Amaximum of one pair of columns can be joined between two tables using the ON clause 
• C、The ON clause can be used to join tables on columns that have different names but compatible data types 
• D、The WHERE clause can be used to apply additional conditions in SELECT statements containing the ON or the USING clause 

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