7. Which two statements are true regarding the USING and ON clauses in table joins? (Choose two.)
A. Both USING and ON clauses can be used for equijoins and nonequijoins.
B. A maximum 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.
Answer: CD
答案解析：
参考：http://blog.csdn.net/rlhua/article/details/12877591
A, USING和ON子句可以用于等值连接和非等值连接,USING不能用于非等值连接，ON可以。
B, 使用ON子句最大只能使用两个列连接两个表.错误，可以连接多个列
C,ON子句用于连接表的列可以是不同的名字，但是数据类型要兼容，正确。ON子句还可以用于联接同一表内或者不同表中具有不同名称的列。
D,在包含ON或USING子句的SELECT命令中，WHERE子句可以做为附加的条件，正确。