hadoop - 如何使用 Hive 将 '\N' 字符转换为空字符串

Question

我有一个包含字段“str”的表。当我运行时

select str from mytable where str is null 

它打印空值。但是当我运行时:

INSERT OVERWRITE LOCAL DIRECTORY "/path/to/dir" 
select str from mytable where str is null; 

中有' \N'个字符

"/path/to/dir"

我想知道在将结果写入本地文件时是否有办法将 '\N' 字符更改为空字符串。

Answer 1

@AshishSingh 回答演示

hive

create table mytable (i int,j int,k int);
insert into mytable values (1,2,null),(null,5,null),(7,null,9);

select * from mytable
;

---

+-----------+-----------+-----------+
| mytable.i | mytable.j | mytable.k |
+-----------+-----------+-----------+
| 1         | 2         | NULL      |
| NULL      | 5         | NULL      |
| 7         | NULL      | 9         |
+-----------+-----------+-----------+

---

insert overwrite local directory "/tmp/mytable" 
row format delimited fields terminated by "," null defined as '' 
select * from mytable
;

---

狂欢

cat /tmp/mytable/*
1,2,
,5,
7,,9