Hive lateral view 和 explode 詳解（轉載）

1. 建表語句結構

create table if not exists employees (
name string,
salary float,
subordinates array,
deductions map<string, float>,
address struct<street:string, city:string, state:string, zip:int>
)
row format delimited
fields terminated by ‘\001’
collection items terminated by ‘\002’
map keys terminated by ‘\003’
lines terminated by ‘\n’
stored as textfile;
2. 表裏 name 和 subordinates 的數據結構

3. 使用 lateral view 和 explode 查詢

select name,subordinate from employees lateral view explode(subordinates) subordinates_table as subordinate;

總結: explode就是將hive一行中複雜的 array 或者 map 結構拆分成多行。

下面就做個小例子, 創建 hive 表 doc, 表裏只有一列 text 類型爲 string, 將 hadoop 目錄下的 README.txt 導入該表, 並寫出 sql 求出 wordcount

create table if not exists doc(text string) row format delimited lines terminated by ‘\n’;

load data local inpath ‘/opt/hadoop-2.7.4/README.txt’ overwrite into table doc;

select word, count(*) from doc lateral view explode(split(text,’ ')) ITable as word group by word;

文章原出處：https://my.oschina.net/zdtdtel/blog/1613715