Hive sql中条件写在on和where的区别

use dmp;
create table dmp.yl_test_1(id int,name string);
create table dmp.yl_test_2(id int,age int);
insert into dmp.yl_test_1 values(1,'aa');
insert into dmp.yl_test_1 values(2,'bb');
insert into dmp.yl_test_1 values(3,'cc');
insert into dmp.yl_test_2 values(1,40);
insert into dmp.yl_test_2 values(2,50);

条件放在on和where后面的区别：
表1
id,name
1,aa
2,bb
3,cc
表2
id,num
1,40
2,50

select * from dmp.yl_test_1 t1 
left join 
dmp.yl_test_2 t2 on t1.id = t2.id and t1.id = 3;

id  name    id_1    age
1   aa      
2   bb      
3   cc      

select * from dmp.yl_test_1 t1 
left join 
dmp.yl_test_2 t2 on t1.id = t2.id where t1.id = 3;

id  name    id_1    age
3   cc      

select * from dmp.yl_test_1 t1 
left join 
dmp.yl_test_2 t2 on t1.id = t2.id and t2.id = 3;

id  name    id_1    age
1   aa      
2   bb      
3   cc      

select * from dmp.yl_test_1 t1 
left join 
dmp.yl_test_2 t2 on t1.id = t2.id where t2.id = 3;
id  name    id_1    age

一、对于left join，如果在on上写a表的条件，则该条件不会生效，依旧会全局扫描

二、对于left join，在on上写副表b的条件会生效，但是语义与写到where 条件不同

三、对于inner join 在on上写主表a或者副表b的条件，都会生效，和写在where里结果一样

参考

hive sql 条件放在on和where区别比较 - 简书

https://www.cnblogs.com/jiangxiaoxian/p/9965978.html