# 增加X自然天
select days_add(now(),2)

字符串转Timestamp

select to_timestamp('2019-10-14 20:00:01', 'yyyy-MM-dd HH:mm:ss');

注意，Impala的timestamp的标准是 ISO 8601  参考：https://en.wikipedia.org/wiki/ISO_8601

两个时间戳比较，粒度是天。否则就自己用2个timestamp相减。

select datediff(to_timestamp('2019-10-14', 'yyyy-MM-dd'), to_timestamp('2019-10-10', 'yyyy-MM-dd'));

Timestamp转字符串函数

FROM_TIMESTAMP(TIMESTAMP datetime, STRING pattern), FROM_TIMESTAMP(STRING datetime, STRING pattern)

Purpose: Converts a TIMESTAMP value into a string representing the same value.

Return type: STRING

select FROM_TIMESTAMP(now(),'yyyy-MM-dd HH:mm:ss') ; 

regexp_replace, 使用正则匹配，剔除非中文字符

select regexp_replace('abcd1234中文你好','[^u4e00-u9fa5]+','') ;

Impala split_part函数

select split_part('a,b,c,d',',', 1) ; -- => a

Impala 授权模型使用记录：

-- 创建角色，角色这个概念，是在Hive和Impala范围的
create role impala;
-- server1是一个默认的配置项
grant all on server server1 to role impala with grant option;
 
grant select on database p2plog to role impala ;
grant all on database p2plog to role impala;
 
-- 这个组对应到用户的LDAP所属组
grant role impala to group impala;
 
-- 查看授权
show roles;
show current roles;
show grant role bigdata_risk;
;
 
-- 表级别授权,撤回
grant select on table xxx_table_name to role role_name1;
grant ALL | ALTER | CREATE | DROP | INSERT | REFRESH | SELECT | SELECT(column_name) on xxx_table_name to role role_name1;
revoke update, select on table secured_table from role my_role;
 
show grant user user_name1 on table hive_table_name1;
show grant user user_name1 on all;
show grant on table hive_table_name1;