【Oracle 12c】最新CUUG OCP-071考试题库（59题）

59、(16-8)choose two:

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

A) The ON clause can be used to join tables on columns that have different names but compatible data types.

B) A maximum of one pair of columns can be joined between two tables using the ON clause.

C) Both USING and ON clauses can be used for equijoins and nonequijoins.

D) The WHERE clause can be used to apply additional conditions in SELECT statements containing the ON or the USING clause.

Answer：AD

(解析：D 答案正确，不管是 ON，还是 USING 子句，都要以在后面再添加 where 子句进行补充筛选;B 答案错误，ON 子句可以连接多个列;

using 不能用于不等连接

using 连接的字段可以 data type 不等，但是名字要相等

using 跟 natural join 是相互排斥的

using 的字段是不能够再起别名

on 连接的字段 data type 要一致，名字可以不一样

where 条件和 on 条件是分开处理的

 

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