Question

我有一张带有字段＆＃39; str的表。我跑的时候

select str from mytable where str is null

它打印为null。但是当我跑步时：

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

有＆＃39; \ N ＆＃39;

中的字符

＆＃34; /路径/到/ DIR＆＃34;

我想知道是否有办法改变＆＃39; \ N＆＃39;将结果写入本地文件时，字符为空字符串。

Answer 1

演示@AshishSingh回答

<强>蜂房

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
;

<强>的bash

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

Answer 2

使用： -

  INSERT OVERWRITE LOCAL DIRECTORY "/path/to/dir" 
ROW FORMAT DELIMITED FIELDS TERMINATED BY "\t" NULL DEFINED AS '' 
select str from mytable where str is null;

如果不需要，您可以删除FIELDS TERMINATED BY "\t"

Answer 3

好吧，你总是可以使用CASE-WHEN语句：

SELECT CASE WHEN str is null then '' ELSE str END;

请记住，您可以使用此表属性更改处理空字段的方式：

“serialization.null.format”

Answer 4

是的，需要小改动。您查询始终返回client_secret结果，因此直接将null放入文件。

" " (empty string)

如何转换＆＃39; \ N＆＃39;使用Hive清空字符串的字符

4 个答案: