配置单元:强制转换数组< string>排列< int>在查询中

问题描述

我有两个表:

create table a (
`1` array<string>);

create table b (
`1` array<int>);

我想将表a放在表b中(表b为空):

and I want to put the table a in table b (table b is empty) :

insert into table b
select * from a;

这样做时，出现以下错误:

when doing so I get the following error :

FAILED: SemanticException [Error 10044]: Line 1:18 Cannot insert into
target table because column number/types are different 'b': Cannot
convert column 0 from array<string> to array<int>.

而如果这些字段仅是string和int类型，则不会出现此错误.

whereas I would not get this error if the fields were only of types string and int.

有没有办法对数组进行转换?

Is there a way to do the cast with arrays ?

推荐答案

使用explode()和collect_list()重新组装数组.

初始字符串数组示例:

hive> select array('1','2','3') string_array;
OK
string_array
["1","2","3"]
Time taken: 1.109 seconds, Fetched: 1 row(s)

转换数组:

hive> select collect_list(cast(array_element as int)) int_array --cast and collect array
       from( select explode(string_array) array_element         --explode array
               from (select array('1','2','3') string_array     --initial array
                    )s
           )s;

结果:

OK
int_array
[1,2,3]
Time taken: 44.668 seconds, Fetched: 1 row(s)

如果要在插入+选择查询中添加更多列，请使用lateral view [outer]:

And if you want to add more columns in your insert+select query then uselateral view [outer]:

select col1, col2, collect_list(cast(array_element as int)) int_array
 from
(
select col1, col2 , array_element
  from table
       lateral view outer explode(string_array) a as array_element
)s
group by col1, col2
;

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