我想在4个Hive表上进行Full Outer Join。 JOIN键是相同的,但4个表的模式是不同的。我想为4个表中的所有id生成所有列值。但是id列只应包含所有值,而不是4次(每个来自一个表)
查询1
select count(*)
from table1 f FULL OUTER JOIN table2 u on f.id=u.id
FULL OUTER JOIN table3 v on f.id=v.id
FULL OUTER JOIN table4 v_in on f.id=v_in.id;
数= 2787037
查询2
select count(*)
from table1 f FULL OUTER JOIN table2 u on f.id=u.id
FULL OUTER JOIN table3 v on f.id=v.id
FULL OUTER JOIN table4 v_in on f.id=v_in.id
group by f.id,u.id,v.id,v_in.id, f.name, f.amt, f.add, u.dt, u.ts, v.ea,v.rd,
v_in.c1,v_in.c2,v_in.c3,v_in.c4,v_in.c5;
数= 2787037
如何从一列中的4个表生成id的所有值以及其他列值?
有没有更好的方法来做到这一点?
您应该只选择所需的列。我想你想要coalesce()
:
select coalesce(f.id, u.id, v.id, v_in.id) as id,
f.name, f.amt, f.add, u.dt, u.ts, v.ea, v.rd,
v_in.c1, v_in.c2, v_in.c3, v_in.c4, v_in.c5
from . . .;
使用full outer join
你需要很多coalesce()
s:
select . . .
from table1 f full join
table2 u
on f.id = u.id full join
table3 v
on v.id in (f.id, u.id) full join
table4 v_in
on v_in.id in (f.id, u.id, v.id);