SQL Hive - 用 0 替换空值 (Hadoop Hive)

Question

进行左连接后，我留下了许多 null（空）值。如何仅在同一查询的某些列中将这些空值替换为 0？

select 
    m1.*, t2.Apple, t3.Berry, t4.Cherry
from
    table1 as t1
    left join table2 as t2 on t1.id = t2.id
    left join table3 as t3 on t1.id = t3.id
    left join table3 as t4 on t1.id = t4.id
;

示例输出

ID  Apple     Berry    Cheery
1   1         NULL     1
2   1         NULL     NULL
3   NULL      1        NULL
4   NULL      NULL     NULL

Answer 1

您可以使用 coalesce() 将 null 值替换为 0s:

select 
    t1.*, 
    coalesce(t2.Apple,  0) as apple, 
    coalesce(t3.Berry,  0) as berry, 
    coalesce(t4.Cherry, 0) as cherry
from
    table1 as t1
    left join table2 as t2 on t1.id = t2.id
    left join table3 as t3 on t1.id = t3.id
    left join table4 as t4 on t1.id = t4.id
;

请注意，这假设所有 3 个水果列都是数字数据类型。

旁注：我修正了您原始查询中 table 别名的一些拼写错误。