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

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.

答案：CD

解析:using 只能用在equiue join ，而且必须列的名字要相同，类型可以不同，但是可以隐式转过去

on 可以用在等或不等的连接上，名字可以不等，类型可以不同，但是可以隐式转过去

A:错误

B:错误，只要名字一样就能连接，不是只有2个列

C:正确

D:正确，where是对结果集的筛选