sql中in/not in 和exists/not exists的使用方法差别

1；首先来说in/not in的使用方法

in/not in是确定单个属性的值是否和给定的值或子查询的值相匹配；

     select * from Student s where s.id in(1,2,3);

     select * from Student s where s.name in( select distinct name from Project)

2。如今来说exists/not exists的使用方法
   exists/not exists是解决两张表的交集和差集

   select * from proj_basic_info p  where   not exists (select * from proj_basic_info q where   p.id=q.id and q.proj_type=1 and q.qy_source='SUAEE')

   select * from proj_basic_info p  where  exists (select * from proj_basic_info q where   p.id=q.id and q.proj_type=1 and q.qy_source='SUAEE')

总结：假设是推断单个属性是是否匹配时。就选in/not in；假设是推断多个属性时，即能够看做集合时。就选用exitst /not exists。