1. out join
   1. where e1.maneger_id(+)=e2.manage_id
2. where condition
   1. where 1=1
   2. where department_id=30
   3. where not (job_id=30)
   4. where amount>100
   5. where order_date<TO_DATA('200-6-15')
   6. where department_id=30 and department_name=sales
   7. where colum=ANY(select colume from t2)
   8. where exists(select * from cities_stores where condition)
3. 采用解析工具
   1. ANTLR
      1. 编写SensorSQL
      2. 自动产生语法树