Hive 中HQL中inner join，join， left join,full join区别
表t1 (id , data)
数据：
1，11
2, 22
3, 33
表t2 (id, data)
数据：
1，11
2, 22
44，44
---------------------------
注意：
join默认是inner join，就是当被join的两个表都同时存在字段的时候才会成功
t1 join t2 on t1.id = t2.id
left join 是两个被join的表，根据左侧表，这里是t1,有的字段来计算
t1 left join t2 on t1.id = t2.id
比如说我们统计两个表相同字段的data的和
如果是left join的话，这里结果是
1，11 + 11
2，22 + 22
3， 33 + null
如果左侧是t2，则为
1，11 + 11
2，22 + 22
4， 44 + null
最后full join代表的是全连接：
t1 full join t2
结果是：
1，11 + 11
2，22 + 22
3，33 + null
4， 44 + null
例子：
join(inner join):
with t1 as (
select to_date(created_at) as create_time1, count(*) as cnt1
from table1
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t2 as (
select to_date(created_at) as create_time2, count(*) as cnt2
from table2
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t3 as (
select to_date(created_at) as create_time3, count(*) as cnt3
from table3
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t4 as (
select to_date(created_at) as create_time4, count(*) as cnt4
from table4
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t5 as (
select to_date(created_at) as create_time5, count(*) as cnt5
from table5
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t6 as (
select to_date(created_at) as create_time6, count(*) as cnt6
from table6
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
)
select t1.create_time1
, t1.cnt1 + t2.cnt2 + t3.cnt3 + t4.cnt4 + t5.cnt5 + t6.cnt6
from t1
join t2 on t1.create_time1 = t2.create_time2
join t3 on t1.create_time1 = t3.create_time3
join t4 on t1.create_time1 = t4.create_time4
join t5 on t1.create_time1 = t5.create_time5
join t6 on t1.create_time1 = t6.create_time6left join:
with t1 as (
select to_date(created_at) as create_time1, count(*) as cnt1
from table1
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t2 as (
select to_date(created_at) as create_time2, count(*) as cnt2
from table2
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t3 as (
select to_date(created_at) as create_time3, count(*) as cnt3
from table3
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t4 as (
select to_date(created_at) as create_time4, count(*) as cnt4
from table4
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t5 as (
select to_date(created_at) as create_time5, count(*) as cnt5
from table5
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
),
t6 as (
select to_date(created_at) as create_time6, count(*) as cnt6
from table6
where to_date(created_at) >= '2018-04-01'
and to_date(created_at) <= '2018-05-23'
and dt = '2018-05-28'
group by to_date(created_at)
order by to_date(created_at)
)
select t1.create_time1
, t1.cnt1 + t2.cnt2 + t3.cnt3 + t4.cnt4 + t5.cnt5 + t6.cnt6
from t1
left join t2 on t1.create_time1 = t2.create_time2
left join t3 on t1.create_time1 = t3.create_time3
left join t4 on t1.create_time1 = t4.create_time4
left join t5 on t1.create_time1 = t5.create_time5
left join t6 on t1.create_time1 = t6.create_time6
order by t1.create_time1full join:
with table_a as (
select t2.city_name, count(DISTINCT t1.bicycle_no) as res1, count(DISTINCT t2.uuap_id) as res2
from table1 t1
left join table2 t2 on t1.operator_id = t2.uuap_id
where t1.dt = '2018-05-29'
and t1.tags = 'repair'
and t1.status = 1
and to_date(t1.created_at) >= '2018-05-04'
and to_date(t1.created_at) <= '2018-05-10'
and t2.post_name = 'xxx'
group by t2.city_name
),
table_b as (
select t2.city_name
, round(count(DISTINCT t1.bicycle_no) / count(DISTINCT t2.uuap_id), 0) as res3
from table1 t1
left join table2 t2 on t1.operator_id = t2.uuap_id
where t1.dt = '2018-05-29'
and to_date(t1.created_at) >= '2018-05-04'
and to_date(t1.created_at) <= '2018-05-10'
and t2.post_name = 'xxx'
group by t2.city_name
),
table_c as (
select t2.city_name
, round(count(DISTINCT t1.bicycle_no) / count(DISTINCT t2.uuap_id), 0) as res4
from table1 t1
left join table2 t2 on t1.operator_id = t2.uuap_id
where t1.dt = '2018-05-29'
and t1.tags = 'repair'
and t1.status = 1
and to_date(t1.created_at) >= '2018-05-04'
and to_date(t1.created_at) <= '2018-05-10'
and t2.post_name = 'xxx'
group by t2.city_name
)
select if(table_a.city_name is null, if(table_b.city_name is null, table_c.city_name, table_b.city_name), table_a.city_name), table_a.res1, table_a.res2, table_b.res3, table_c.res4
from table_a
full join table_b on table_a.city_name = table_b.city_name
full join table_c on table_a.city_name = table_c.city_name
order by table_a.res1 desc