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 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 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3题：

第4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5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6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7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8题：

第9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10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.