using等价于join操作中的on，例如a和b根据id字段关联，那么以下等价

using(id)

on a.id=b.id

以下2个实例等价：

select a.name，b.age from test as a

join test2 as b

on a.id=b.id

select a.name，b.age from test as a

join test2 as b

using(id)