impala: 类似hive的array_contains()函数

• 首先，需要先了解impala中的两个函数的作用，一个是group_concat(string s [, string sep]), 一个是find_in_set(string str,string strList)

1、group_concat(string s [, string sep])
按照指定分隔符, 将多行记录的 s 表达式结果拼接起来, 结合group by 一起使用

	select id,group_concat(name,'##') from (
	select 1 as id,'zhangsan' as name
	union all
	select 1,'zhangshu'
	union all
	select 2,'wangwu'
	union all
	select 2,'wangsan'
	union all
	select 2,'wangbu'
	) t group by id
	
+-------------++-------------++-------------+
| id          | group_concat(name,'##')     |
+-------------++-------------++-------------+
| 1           |zhangsan##zhangshu           |
+-------------++-------------++-------------+
| 2           |wangwu##wangsan##wangbu      |
+-------------++-------------++-------------+

2、find_in_set(string str,string strList)
查找某个字符串在一个以逗号为分隔符的列表中第一次出现的位置（以1为起点），如果查询不到或查询字符串中出现’，’(逗号)，返回则为0

--在以逗号间隔的abcdefg中字符c第一次出现的位置
[master:21000] > select find_in_set('c','a,b,c,d,e,f,g') as find_in_set;
+-------------+
| find_in_set |
+-------------+
| 3           |
+-------------+
--在查询'，'的位置时的返回值
[master:21000] > select find_in_set(',','a,b,c,d,e,f,g') as find_in_set;
+-------------+
| find_in_set |
+-------------+
| 0           |
+-------------+
--在查询不存在字符的位置时的返回值
[master:21000] > select find_in_set('h','a,b,c,d,e,f,g') as find_in_set;
+-------------+
| find_in_set |
+-------------+
| 0           |
+-------------+

两个函数结合实现类似array_contains() 的效果

select id,group_concat(name,','),
	find_in_set("zhangshu", group_concat(name,',')) as res1,
	find_in_set("wangsan",group_concat(name,',')) as res2 
from (
	select 1 as id,'zhangsan' as name
	union all
	select 1,'zhangshu'
	union all
	select 2,'wangwu'
	union all
	select 2,'wangsan'
	union all
	select 2,'wangbu'
) t group by id

+-------------++-------------++-------------++-------------++-------------+
| id          | group_concat(name,',')      |    res1      |   res2       |
+-------------++-------------++-------------++-------------++-------------+
| 1           |zhangsan,zhangshu            |      2       |     0        |
+-------------++-------------++-------------++-------------++-------------+
| 2           |wangwu,wangsan,wangbu        |      0       |     2        |
+-------------++-------------++-------------++-------------++-------------+

最后再结合if函数，就可以实现类似的功能了